This may be useful for the FAQ and could be valuable information for people in some states (including mine).

The person I spoke to has worked for Okay since 1986 and to the best of his knowledge these practices were in effect going back to that time.  

All Okay manufactured magazines during the time in question have markings on the outside of the magazine body (he is not 100% sure this goes to 1986 but does apply to ban years +).  These markings include a company name and possibly logo (Okay, Colt, etc.)

On the inside of the magazine body, there are two halves.  On each half is a letter (O on one side and K on the other), followed by a number (e.g. O1 on one side and K1 on the other side).  Below those are a two digit year code on both sides.

So an Okay Magazines made on January 2006 would have the following markings on the INTERIOR of the magazine body:

One side:
O1        
06

Other side:
K1
06

Before 1986, this does not apply.  I showed him magazines marked as follows:

One side:
O3

Other side:
K2

And he was not able to tell me what those codes mean, except that if they are Okay magazines then they are pre-1986 (he was not sure and remarked that he has seen counterfit magazines before).  The O and the K are obvious, but what the numbers mean is anyone's guess.  He said the person who would know is unfortunately deceased.

As I said, this may be useful for people in ban states.   All post-ban Okay magazines have markings on the outside of the magazine body and year codes on the inside.

Your info is wrong. I've checked it against hundreds of magazines.

The "O" or "K" stamp refers to the month of manufacture. You would have a stamp like "K9" and then another stamp that would say "91", this would be a mag made in Sept. 1991. I've gone through hundred of my Okay mags and any of them that have this type of marking system all check out with the info I just mentioned.

Can you post pics of your "O" and "K" marked mag? I've never seen an Okay mag that has marking on both side of the mag body internally, only a single side.

What you said matches what I said (or rather the Okay Industries person said) except that you say you only see it on one side.

As for my own preban mags, here are links to the images:

Side 1

Side 2

They are too big to display here.

As for current or "post ban" magazines, I can't give you a picture since I don't have any, they are not allowed in my state.  I can only go based on what Okay industries told me.

Every single Okay mag I've seen - from 1980's to 2008- have been marked on both sides (inside)

Based on what info I've been able to find, it works like this.  Prior to 1986, mag bodies were marked on each side, on the inside.  O with a number on one side, K with a number on the other side.  1986 up, they are marked with the year, as well as the above markings.  You might see 87 over K4 on one side and 87 over O4 on the other side.  Prior to 1986, you'd just see K4 on one side and O4 on the other.  I have Colt floorplated, OK manufactured pre-ban mags with the markings K1 O1, and K4 O4....no year, no outside markings at all.  They obviously weren't made in 2001 or 2004, or they would be ban marked on the outside of the mag body (LEO/MIL only, and year), so I'm not really sure what the number itself means, but I strongly suspect the above poster is correct about it being the month.  

You could have a magazine like the one pictured above, with two different numbers on each half......as the halves aren't necessarily stamped (and therefore marked) at exactly the same time before being assembled.  The one above has a 2 on one side and a 3 on the other.  Perhaps one half was stamped on the last day of Feb, and the second half on the first day of March?  Dunno.

Doh.  That didn't even occur to me when I was freaking out about seeing "02" on the inside of one my new old stock magazines.  :)

You are right, I had a mental relapse.

One of the letters represent the month and the other the year.

I believe the K refers to the year, so K2 = 92 and the O to the month.

From what the Okay rep told me, the O and the K are for "OKay Industries."   Every single Okay mag I have has the O and the K and I have 22 of them.

These are pre-1986, so it's likely the 2 refers to 1982.  1986 and later are year stamped as well.