What do you know about this air rifle?

[trg42wraglefragle]

Hello all.
Ive got an old air rifle at home and was curious to know what it was and how old it was.
It doesn't have a serial number anywhere, just Gecado Mod. 27 on the top of the receiver (or whatever its called on an air rifle), and Made in Germany on ther left hand side of the receiver.

If anyone knows anything about this i'd be grateful to hear.
Thanks

 

[mapsjanhere]

Google Diana 27, Gecado is just one of the many brand names it was offered as. It's been made since 1910. Looking at the pictures it looks very much like my first air rifle, about 1975.