Have you seen them drop or are you just guessing? Strange Coins are hard to come by these days, so I'm not wasting 31 for a ton of duplicates. Aside from the new guns that I have yet to receive/unlock, pocket infinity is the only year 1 gun that I need still.

I have no idea, I'm not on often enough to find out, but I've not seen any vanguard mentor missives or even the embalming orb from Eris, so I'm gonna assume the only way to get the weapons that were attained via bounty/progression (Invective, pocket infinity, Nechro, etc.) is via the engram.