Have a few myself Ian, They came with two bottles and in all flavours from .177, ,20, .22, .25. with 1,2,3, or 4 barrels, Whatever you ordered. My first one came new with .177 and .22 barrels, Second one came from my friend Guy with .22 and .25 barrels and the rest had single barrels of various cal`s.
No spares available at all these days and have to be made or upgraded especially the terrible valve system. Luckily mine have been ok and seals are easy enough to match up, Only try and buy ones with two barrels although you can have a blank and probe made up easy enough, Try Dave Mercer...DM80 on here or if you would like to speak to Martin the inventor for a chat then message me and I will send his number.
Nothing more to add for a collectors rifle, Would I use them again for hunting?... They put bunnies on the table and so have all my other rifles but my rapids are my go to rifles. Price,,,,, Well they are up and down like a prostitutes knickers and if one comes along they don't usually hang about for long.
Wonder if I should sell mine,,,,,,,Probably not. Col.