Both the Marlins I have are MM generation, will take apart to look at the pins today if I get to it, in the meantime here is a craptastic picture which shows the QR code on the one I bought NIB from Big5. that little box to teh far right next to the H in the SN pretty much looks like a QR code but the resolution of it is pretty darn low even in person.
Untitled by
rkt88edmo, on Flickr