So a few weeks ago I put the word out at work that I was looking for pistol options to see what might be out there. Today a guy from another station let me know he has a Ruger MKI, stainless, with the short tapered barrel. He said it is the "Signature Model", still in box, unfired, papers, etc. I've always liked the look of that model as it sort of looks like a Luger. I shot a similar one maybe ten ago and I remembered really liking it, but I'm pretty sure it was a newer one, and it had the longer heavy barrel.

The only thing I've found is that supposedly the early 9 round magazines were flaky, but if I understand correctly new ones will work in it after taking them apart and reversing the thumb button.

He said he bought it on a whim like 20 years ago, took it apart to clean it, and couldn't get it back together. Some years later he found it a closet, and after a bunch of swearing finally got it back together correctly. Supposedly he never shot it, just set it back in a closet where it's been sitting. He said he will take $300 for it so I suspect I'll probably get it, if so this would be my first 22lr pistol.

Are there any pitfalls to the old original ones?

If you get it and keep the barrel,  you have to use the "lollipop " site method, not "sites-on-target", some ppl don't like this, should be able to find mags and it might be possible to make mkIi mags for.

Also good luck taking upper off and putting it back on. It takes a knack to get it

I paid just under $300 OTD for a brand new 22/45 MKIV last during the panic. No way in hell would I pay the same for a MKI or any previous generation that’s an absolute bitch to get back together, after owning a MKIII I actually wouldn’t pay anything for one lol.

I  got a Ruger Mark 1 (mom bought it) in 1968  short thin barrel about 4 in.  I shot countless thousands of rounds through it mostly at snakes in South Texas. They work just fine.  The magazines are still available directly from Ruger.
LINK
I have owned every generation of Ruger Mark series pistol the Mark 2 is my favorite because I dont care for the side cut out of the Mark 3 and the 22/45 is the worst of them to try to re-assemble because it requires having the mag in or out for a portion of the process. With the Mark 1 and 2  you have to understand that there is a small bar that hangs from the back of the hammer and if it catches against the little cross bar rather than going over it then it is not together correctly.  
To idiot proof re-assembly LINK TO PART  

Link to video to disassemble and reassemble   Buy with confidence they are excellent training tools and $300 is a bargain.

22/45  re assembly  Putting these things back together requires one understand gravity. They are a thinking mans weapon.  The reason you turn them upside down is to use gravity to position the hammer and the bar that is on the back of it but buying the part above ends your frustration.

Note there is a small spring and attached tip under the firing pin when taking it apart note the correct position of that part and do not loose it.

Mark 1 series mag release is at the bottom back of the magazine (European style release) like an H&K P9s  it's a very positive retention system.

No pitfalls, buy with confidence. I have a 62 model with the rare factory comp I got for doing a day of work for a friend and I've been competing and winning club matches with the gun. It's a little beat up but still outshoots me.

They are great little guns. I found one a couple years ago at a funshop for $65.

The take down is different, but after doing it a few times, it's not bad.

If he bought it new 20 years ago I question if it’s actually a mk1. I bought my mk2 easily 30 plus years ago. Is it the standard or the target model? I have my fathers mk1 target he bought sometime in the early 50’s I think. It goes well with my mk2 and my 22/45 lite.  Excellent guns and the takedown/reassembly is pretty simple once you’ve done it a few times. I recommend not cleaning them any more often than needed (when they start jamming) as you can loosen the reciever/frame fit.

I went ahead and grabbed it
It looks spotless and was in both of the special edition boxes with all papers just as he said.
I figure for $300 I couldn't go wrong.

Nice and stainless to boot. Yea, I wouldn't have hesitated.

Check out pac lite uppers if you want variety

Nice gun.

A year ago $300 for it would have been a little high but between it being about unused and stainless and demand being stupid at this time it is a great deal.

Some folks get all excited about the takedown but in reality you don't have to break it down that often . When I have/want to do it I look up directions and review before I do it and it goes fine. Directions in the Ruger manual are lacking , go to other sources

1 of 5000 ruger pistols sold from $400 to $1000 on gb recently.

Example

Shot my first Ruger Mk1 5.5" bull barrel in about 1980 or 81.  Amazed that I could stand there and put the next bullet in the same hole the first bullet went into at 10 or 12 yds.  But my brother wouldn't sell it to me so I ended up trading my Ruger Single Six in on one a year or so later.

Same kind of accuracy.  Our youngest brother said he never knew a pistol could shoot like a rifle till he saw us shooting those Mk1 5.5" bull barrels.

Magazines?  Yeah, as posted earlier, you can still buy them.  Problems with them?  Not mine or any of the others I know of (also a couple of the skinny/tapered short barreled Mk1s in the family as some of them didn't feel the need for adjustable sights, but they are all Mk1s).

We used to squirrel hunt with ours.  Head shots.  And, mine really liked Remington Thunderbolts back in those days.  Plinked with them and hunted with them.  No idea how the "newer" Thunderbolts would shoot in it.

Good luck with it.  Great little pistols and loads of fun.

Easy to put together once you figure it out

Trick of camera perspective, or is that barrel oval?

I've owned a couple of MKls, and while they're ok, I found the MKll to be much better. Personal preference only.

Rugers are not shaped like that , the photo for whatever reason is twisted.

Nice gun .

I find the short taper barrel to be a bit light forward and slightly more difficult to shoot than the bull or long taper ones . Possibly that is just my preference but it wouldn't have prevented me from snapping up that deal

Same here... The MkII 5" bull barreled version is my favorite of all of them. Had a MKIII polymer, threaded barrel... total piece of shit with a Winn-Dixie quality trigger. Sold it within a month. MKI's are my 2nd favorite of the series though.

My vintage MkII from 82' I believe only came with 1 magazine. Works flawlessly... Bought (3) supposedly OEM 10 round mags from Brownell's and they are/were the shittiest jamming magazines I've ever contended with. I reworked, re-profiled, and india stone'd the lips smooth to match the OEM original magazine's feed lip shape and now they run flawlessly. The 3rd no matter what I do just won't run even though the feed lips match the other's perfectly and are de-burred/baby smooth.

I won't be purchasing any more "Ruger" magazines from Brownells. OP, I suggest you source true OEM vintage magazines if you can.

Original 9 round mags are solid, IMHO better than any new replacement mags.
I’ve got a ‘64 MKI that’s been in the family since ‘66. Solid shooter. Never broken or jammed.
Not many rimfires that even come close to a MKx trigger, getting an old one that’s got some wear is better.

I’ve tried Triple K, Ruger & Mecgar replacement mags. The original factory 9s are still my favorite and Grabbed a bunch when they were still obtainable for under $40. Even those old zigzag springs are still like new. Not sure if there’s ever been an aftermarket replacement for them.

If you have mag issues, check the feed lips. Since there’s no feed ramp, the mag is doing all the work. Unless they’ve been dropped, it’s usually not an issue.

Like the OP, I like the look of the tapered barrel, and since I’ll never afford a Luger, this is a poor man’s alternative.

Yeah, personally I wouldn't shoot that one. There are collectors out there that would love to have that gun in NIB condition and are willing to pay well for it. I would sell it to one of them and get an MKIV version and use the left over funds for something else.

Congratulations, I hope you enjoy it. Personally, the new Mark IV that I bought and the one-button takedown is a really great design that I really enjoy.
I had an original Mark 1 and a handful of those old magazines and several of them did not work.
Before the Youtube and the internet, putting a Mark 1 together was not easy and I also found out the hard way.
I have joined the new gen, I'm not going back.

Nice pistol.  I think I read that the ones with the red medalion in the grips were some of the first pistols that Ruger made.  

Keep it all as is, and maybe sell it for big bucks later.

A used Mark II, 5-1/2" bull barrel, was the first pistol I bought, in 1988 for 200 bucks.  Still have it and love it.

Personally, I never found the takedown of it that hard, and while I had to fiddle with things at times if I forgot exactly how to put it back together, I never painted myself into a corner with it.

My steps:

To take apart, it has to be cocked.  Remember it this way - you generally don't want to dry fire a .22, so you have it cocked to take down, unlike a Glock that you have to dry fire.

Take a small flat head screw driver, cover with tape, and pry up the amembly level.  Undo, pull "backstrap assembly" down and out.

Bolt out.

Upper from lower.

Clean and lube.

Upper on lower.

Bolt in.

Pull the trigger, to get the hammer and it's strut out of the way.  Move "backstrap assembly" in and up through bolt.  If it won't go in, the hammer and strut are not in the right place.  Fiddle with, till "backstrap assembly" is locked up and into the top of the upper.

Now point up at a 45 degree angle or so.  The strut need to get pressed into the "backstrap assembly" when you swing that into place.  Tip - if there's not a bit of spring style resistance as you swing the "backstrap assembly" into place, the strut isn't in the right place.  The "backstrap assembly" needs a bit of a push at the end to get seated and compress against the struct, then swing the locking lever back to lock it back in place.