Can you print the serial number? I know what you said before and I'm not challenging that. I do think you might have the size wrong. You said it's 56 cm, but it looks like a 52 cm. I have had several 52's, I can tell that by eye, usually, but I'd like to confirm. Plus I'd like to see what tubing it is. If its a 56 cm I might want to take the frame off your hands, then you can go look for a real 52.

But I do think that is actually a 52 (20.5"), which means to fit you would need a Trek 19 inch.

Could you please also measure the seat tube length, center of BB to the top of the seat tube? inches are fine, if you like.