Webley Mk VI R.P stamping

I've been curious about this "R.P" stamp on the backstrap of my Mk VI for quite a while. Found a lot of bullish on the interwebs, but little was plausible. I'm guessing something like "Regimental Provost", or "Regimental Police", but guessing is the operative term here. Perhaps one of you knowledgeable chaps can help me solve this mystery. Thanks!

Perhaps I'd better sell it. Looks like one with the same marking went for $4000.00 on GB in April. Seems that "R.P" designation indicates it was issued to WW II RAF Squadron 288, according to the description. Remarkable.