Not sure how many of these are original, or faked c broad arrows, but they are around... It should also have the LB stamp as well. Longbranch re-barreled an unknown number of #1 MkIII rifles at the very beginning of the war as the arsenal was brought into production. The heat was on to "put rifles into hands" and so re-barreling No1 MkIII rifles - of which fairly large numbers were in the Canadian forces' arsenals, was an expedient solution. They were, from what I gather, largely lefotver rifles from the end of the production runs near the end of WWI, that were then used for training rifles between wars. As a result, they were pretty thoroughly shot out, with not much rifling left, so Longbranch was given the ones with the best condition receivers to re-barrel.
I have one with all the right stamps on the receiver and barrel to match this history (it was actually a gift from a friend), but after WWII, Bubba got hold of it and... Well... I've got most of the parts tracked down to bring it back to its former glory, and it's going to be my winter project.
At some point, Smellie will likely poke his noes in here, correct my errors, and dump some much better info.
They're interesting rifles, with interesting history. If you have one of the real ones, cherish it. They're effectively "Two War" rifles.