The 81 refers to the rating used by Pecar for measuring 'twilight factor' or the ability to use the scope at low light.
Hence 8x45 for a 40mm objective etc.
Here is a link with some info. Eagle Hurst Sporting | Pecar Berlin
I have a few Pecars including two 4xJr but I won't part with them for the world. They are too good compared with modern massed produced glass. Not all the reticles are interchangeable depending on the model of scope.
I emailed S & B and and asked them if they had taken over Pecar and do they do Pecar repairs. I received a reply from a Klaus Gorzel in their service Department who stated they had not taken over Pecar and that I contact:
Gruner Weg 14
Tel 0049 (0) 6441-28692
Telefax 0049 (0) 06441-26432