What do you plan on using for your bulk CO2 source?
If your bottle has a 1/8" NPT (National Pipe Thread) fitting it should work. Otherwise, you will need an adapter to connect the female 1/8"NPT on the gun to a paintball tank.
It's possible the pistol was sold by Sears or Montgomery Wards, hence no Crosman logo on the pistol. ID would be on the box and paper work.A modern paintball CO2 tank is the best way to go for filling. If you get her working you will find that these are well made, accurate arms. Dave
Sears and Montgomery Wards were American department stores. You could go in and get new tires, a gun, ammo, tools, some new clothing and pretty much everything else except uncooked food. Unfortunately, they're now both a part of the past.At one point Sears even sold pre-fabricated houses from their catalog.Stay safe,J~
Its not a model 115.Its an early model 111. Pre 1950 1/2 bulkfills have no Crosman logo, and earliest guns have no caliber stamp or serial or model number.