Maybe like a Para-Fal, hide it in the feed tray cover somehow?
Also, note the bipod - looks suspiciously like a FAL's
I bumped up the size of the original
Working left to right, I see : no evidence of a stubb buttstock or recoil assembly tube under his right hand - there's some funky semi-circular metal assembly just forward of the ejection port and his left hand grips the legs of a bipod (I thought FAL, but it might be a DP28 - look at the big round pivot points under the front sight) and at the muzzle brake looks like an AK47 slant.
Besides the gas block, I don't see a whole lot that looks like an RPD....
From left to right, recognizable RPD features : box receiver, cocking handle (folded up), ejection port, rear sight and 'hump', then the front two-point mounted gas assembly.
Looks like someone grafted an AK front sight onto the flat top of the front gas assembly ring.
No forearm, obviously, but that looks like a FAL or AK47 pistol grip.
Still can't figure out what the 1/4 circle assembly is, in front of the ejection port.
Damn another one I am going to have to put on build list...
Could the "1/4 circle assembly" be a recoil spring, in tension?
wish we could find more photos of the "pistol" version for better identification