Speaking to
Canadian
Service shotguns, we had no additional military stampings, proofs, or identification markings, they were only marked with Remington roll marks and typical serial numbers.
During my time (subject to change with modernization) we had the Remington 870P (Police) parkerized finish with composite stocks. 12 guage, 3" chambers, cylinder bore, bead sight. barrels at 18" if memory serves. Two butt stocks were offered, the typical fixed composite, and the over top steel folder with pistol grip.
Identifying a former service one in the future will be difficult because only the serial number records will tell you if was a CF gun, but due to currently policy it should be fairly easy as all former CF weapons are to be destroyed and not sold out of service.
https://www.milsurps.com/images/impo...bc86353b-1.jpg
https://www.milsurps.com/images/impo...m870law4-1.jpg
Additional remarks.
The LOP was too long for anyone under 6'2" to shoot properly with body armour on, personally I couldn't even shoulder the weapon while wearing plates, well I could, but then I couldn't reach the pump with the supporting hand, it looked comical I must say...
The folding steel stock was the worst thing I have ever tried to shoot with, I would rather be hit in the head with an entrenching tool than do another "Jungle Lane" range with one of those.
There was a great deal of mistrust of these shotguns, first because of a warning officially issued around 2004 that stated our shotguns were found to discharge if at the ready (shell chambered) and the weapon suffered a short fall (drop) onto the butt, secondly due to lacking a removable magazine the positive clearing of the weapon became different than most weapons, which lead to a run of ND's among less diligent soldiers unaccustomed to shotguns in their former civilian life.
During my tour to Afghanistan in 2006 our shotguns were issued with #7 birdshot high brass loads, since there were few upland game birds in the desert, this ammunition became a running mockery of the supply system among knowledgeable shotgunners.
Shotguns did not really see widespread service, they were issued during special situations and during operations generally rode inside the LAV 3 and were used to provide a measure of "seriousness" to leaders meetings (Shura) after Captain Greene was nearly killed with an axe during one these kinds of meetings.
I will find some period photos from my collection to share.
I see from the internet, different types of shotguns have entered service, some are 870P with extended tubes, sights, or flashlight pumps, the JTF2 apparently has a Benelli but that is outside my immediate scope of knowledge.