At first inspection this looks like an ordinary R.E.L. CGB 57G.A. 7x50 examples of which are commonly seen. However, a closer inspection reveals a Bausch & Lomb 1942 serial number on the hinge end cap (UV7509, the U letter prefix indicating 1942 manufacture). I don't believe this is simply the case of a B&L end cap being retrofitted to an REL binocular because RCN inventories list 35 REL 7 x 50 binoculars with dual serial numbers i.e. an REL one and a B&L one. The RCN inventories also list 100 7 x 50 binoculars with solely B&L serial numbers which are almost surely U.S. Navy Mk I 7 x 50's. It my theory that either:
1) circa 1942-1943 REL acquired binoculars from B&L to meet contract orders they could not fill (as I believe was similarly done with the dual marked REL/Universal 6 x 30 binoculars) or more likely
2) early in the war before REL was able to supply binoculars, the Canadian Navy acquired numbers of B&L Mk I 7 x 50's some of which were subsequently retrofitted by REL with dry air ports (as was also done with early made REL CGB 54's and 57's which were not originally equipped with dry air ports) and given REL markings and serial numbers at the same time.
These dual serial number marked binoculars in the RCN inventories have puzzled me for a while and I am glad to have finally found one.
Your first theory is the one I'd go for Frank - now I'll have to recheck my own! ;)