I have a RWS Original 45 in .177 cal, the rifle is in a mint/unfired condition, after a little reserch and gunsmith help, i discover that the rifle is in a pristine condition. The rifle was manufactured on 11/81, is the older model with the leather piston seal. When i cook the rifle the spring gets very noisy and when i fired it, there is no twang but a little bit of dieseling. The spring are totally dry but that doesn´t surprice me because the rifle was boxes for 25 years. I think that a little bit of moly grease and tar will be very helpful, but i don´t want to damage the finish, so what do you think, lube or not lube the piston seal and spring? I´m not gonna shoot the rifle a lot so i think maybe a little bit of chamber and spring oil will do the job.
About 2 years ago I purchased a new old stock RWS-45 like yours. Mine was a 1984. Upon tear down and inspection it was very dry inside. I would highly recommend that you have the gun inspected and relubed. These old guns are sure worth the extra time and effort. You will be glad you did.
Chris