It's an HFC HG-131 gas airsoft that I found online for about $40, so it was about $100 less than the Tanaka M10.
It doesn't have a tapered barrel, the correct grips, or the correct trigger guard profile, but I'm pretty happy with it. I sanded the grips to knock off the shine and give them a slightly weathered look, and did a little drybrushing with Testors gunmetal all over the rest of the gun to make it appear it had seen some adventure.
Enjoy!

Without flash:



And a couple with flash:

