The AN/PVS2 was the 2nd version in the 1st generation "starlight" or passive NV scopes used by the US military, there was the AN/PVS1, followed by the AN/PVS2 in 3 variants, & the AN/PVS3, each was smaller & lighter & a bit more electronically advanced than the preceeding model, the AN/PVS1 came into service approximately 65-66, the AN/PVS2 approximately 68-69, the AN/PVS3 was just coming into service when we pulled out, 73-74. As stated in the above replies compared to todays NV they're heavy, crude, tempermental & the 1 & 2 models were a PIA to carry in the field, they did in fact mount off to the left on both the M14 & M16 & were "odd" to shoot due to the eye positioning, an instructor showed us a trick though (only applicable if your weak eye wasn't too different than your strong & the rifle was set up for it), on the M14 using your left eye allowed for an almost normal cheek weld, not a perfect solution & never "officially" sanctioned but a "field expedient" LOL! The AN/PVS2 came in a metal transit case w/spare batteries, tools, manual, carry strap & field carry case:
The metal case wasn't used in the field, it was a storage/transit case, the system was big/heavy enough in the field. There was this mount for the M14:
and another for the M16:
Here's a coupla pics of the AN/PVS2 on an M16A1 replica (for the "sharp eyed purists" the M16 shown is NOT a correct A1, it had an A2 lower, it's been totally rebuilt & corrected since, just haven't had the chance to get new pics!) to give an idea of what it's like:
and on an XM21 replica:
As said in earlier replies these scopes are "old" school & don't compare very well w/newer NV but they were the best there was at the time! These were 1st generation "passive" NV devices, meaning they did not emit any kind of electronic signal & were virtually undetectable, at least at that time. Looking at them today they're heavy, cumbersome, short ranged etc but they were "star wars" gear back then!
Keep in mind these NV scopes replaced the original IR (infra red) "active" AN/PAS4 NV sets:
Shown above in it's metal transit case & on the XM21 replica, these NV scopes were basically updated versions of the WWII era M1 Carbine "sniperscopes", the main drawback (besides being even larger, heavier, more cumbersome & requiring carrying a very seperate battery on your belt to power the IR emittor than the AN/PVS2), these were "active" NV gear, meaing they actually emitted an electronic signal, IR light, from the large round fitting on top of the electronic scope, this IR light source was very simple to detect using very simple electronics!, the AN/PVS2 on the other hand is a "passive" device, meaning it does NOT emit any electronic signal, it works by taking existing "ambient" light & electronically "intensifying" it inside the image intensifier tube, it could not be detected by an enemy. The drawback (at least to these 1st generation starlights, I don't know about the newer ones), is they required existing light, ie:, moonlight etc, if it was pitch dark, overcast, moonless etc they didn't work.
We were issued an AN/PAS4 NV set in 1971 on arrival in VN, used w/the XM21, we thought we were "invisible"!, in early 1972 we saw a Soviet SVD Dragunov that had been captured & were shown the PSO1 scope it was equipped with, when the SVD was adopted in 1964 it's standard daytime scope the PSO1 had been designed w/a built in IR detector! to give you an idea of the simple electronics needed to detect "active" IR NV here's a pic of the PSO1 scope & the scope on an SVD:
The above pic shows the IR detector built into the PSO1 scope, the round window facing up in front of the top dial is the power source, sunlight!, the small switch just behind it on the side is the on/off switch, at night, flip the switch to on after powering it w/sunlight & if the scope is looking at an IR source the source will glow green in the PSO1's crosshairs!
Above is a side view of an SVD w/PSO1 scope mounted to give an idea how small & light this "detector" gear was. 2 weeks after seeing the SVD/PSO1 we were issued/trained on the AN/PVS2 & it was a pretty comforting feeling, again!, of course 30yrs later when I started researching some of this stuff I found out the starlight scopes had been in service since 65-66 & we were issued an AN/PAS4 IR set in 1971!
The M14 & M16 mounts shown in the pics above mount both the AN/PAS4 & AN/PVS series NV sets.