Telescope Reviews: Pentax IF 7x50 Marine

Hi all

I am looking for some information about an old Pentax IF 7x50 Marine model, some information about their optical quality (despite they are a fully-coated and not multi-coated one), etc etc.
They are not ''rubber covered'' as the modern PIF model - they are similar (more or less in appearance) maybe with the Nikon IF 7x50 Tropical or the Fujinon Meibo 7x50.
They are waterproof and comes engraved on it left metallic prism cover ''Pentax'' and on the right cover ''Marine -Fully-Coated 7x50 field 7.1º''.
It case is similar to some old Pentax models - a black (leather?) case with red velvet inside it - on it box (white and green in color) comes written 7x50 BIF Marine.
I would appreciate any kind of information since I bought one of this in really brand new condition (but I have not they here yet).

regards Pedro