I have one of these frogs as well with the same marking. My frog however is the version without the hilt retention strap. It is made exactly the same with the pouch being constructed of a lighter weight woven material than the body. If memory is correct, mine has more of a brownish sand colored body with a lighter tan pouch. It also has the same white cotton thread to include the unusual horizontal line of stitching at the bottom of the belt loop. The marking is in the same location and I believe it to be REP 43. The reason it is in upper case letters is because it is not a three letter code. Rather it is the maker's trademark from an unknown producer. Same as the upper case letter trademarks sometimes found on canteens, mess kits and other items. Have seen only a very few examples of these frogs and all have been 43 dated. The one from my collection is pictured in the reference section under late war and tropical frogs. I will try and take some better photos to post here for comparison.