No worries, man.. No offense taken at all,
The primary thing to keep in mind is that all parts back then were hand machined, and in a rush too..due to the war and whatnot. So all parts are almost guaranteed to vary...you might get lucky sometimes though..
Even the Mauser made immediately after the 2813, on the same machine-line likely had many variances even if being made by the same people, machines, tools etc.. But the modern manufacturing with CNC has cut that variance down to negligible at least these days.
The first thing to note on the PS/RIA FH is the bullet knurls at the rear/bottom of the part. The only ones we have seen here real in-hand or in photos always used a radius cutter for those cuts creating the 'egg' like parabola shape at it's point, not a ball-endmill as per this FH and many other replicas of the past before it became a standard to use a radius cutter or mimic it with a six-axis machine (which these days can produce an almost identical result aside from the swirl by the direction the cutter is spinning).
Also the smaller knurl across the main body of the FH (which still vary quite a bit on real ones) also looks to be CNC as well, rather than an actual knurl tool basing on the count of lines and the overly even, though incorrect, depth, spacing and lack of expansion that a knurl tool would cause. Kurling tools can be designed to 'cut', but they're fairly uncommon in this use. Most just displace existing material rather than actually remove it. Causing somewhat identifiable displacement markings per knurl, most noticeable towards the ends of each knurl line.
The biggest way to see it is by looking at the length and the taper the small knurl's have towards the front large radius before the cone, vs. this and most replicas as this one appears to be.
Also a notable lack of the manufacturing transition to the cone after that primary radius. Note the radius and transition differences between the primary neck radius' and the cone section, they're are not accurate to any known real FHs as of yet as far as what's been seen by the community (as far as I know) pertaining to MG81 FHs. There's a notable amount of tool changing there, possibly a turret lathe to save time, or just machine to machine, but who knows? There's a short flat transition between the cone and the primary radius/body of the FHs that have been seen on most real ones, some more noticeable than others, but the Hero's real MG81 FH clearly shows it pretty well. Even to the point of the flat lathe portion of the transition to the cone being a tad too deep on the Hero's, just a little, but something visible and worth adding to our replicas. Pat added that on his too I believe, as per the Hero's.
The other issues are the cone being very clear of any hand machined marks, very smooth and would take an Etch-A-Sketch master to do by hand back then without leaving some machine marks behind (I don't doubt that a machinist hasn't accomplished that sort of skill though..I'd actually like to see something like that in person to be honest =b), but doubtful and unlikely to be seen on rushed machined FHs for wartime. It's possible, but still unlikely to expect I think..
Basically it's the lack of the radius cuts at the bottom/back of the FH, and the lack of the tell tale signs of hand machining being present, in a rush or not even. I think both knurl types and results are the smoking-guns though as far as authenticity goes for this FH.
-Carson