Many Bergs end up parted out and cylinders are not exactly what need to be replaced most of the time so it's not a surprise you got it in a box. Would not be surprised it was on eBay a couple times.
As I said on TT, $20 would be a good start and see what happens. Unlike what I said on TT, a reserve would actually be a good idea and then you give second chance to runner up if the highest bid is satisfactory.
Otherwise don't forget the part number.