The G55 is quite rare; I have only seen one other apart from mine which is in near-perfect condition with all original parts and in .177 cal. and shoots well and the tap is auto-opening. I paid £190 for it 10 years ago. It also came with a period 1950's 'scope which I think I paid extra for but the rifle alone I would think is now worth about £200-£240.
HOWEVER if you have removed the 'scope rail, re-blued it and had to re-finish the stock and it is shooting weakly, although it is rare I would guess in that condition and in the absence of pics it is probably worth about £70-£100, but just my opinion.
Aubrey