NOTE: Since writing this, others made me aware that etching PVC is bad for the chlorine gas. So, don't do this. I'm still leaving it up for the idea of using records as letters, however, because that worked a treat.
Step 1: Get Some Records
But look at these gems! A Star is Born? Christmas with the Canadian Brass? Free to Be You and Me?
OK, I admit that I've never listened to any of these although Free to Be You and Me seems to have some huge nostalgic value for my friends. Whatever... it's time to destroy them.
Step 2: Etch!
Here, I laser-etched the records, but that's not recommended for safety reasons. I'd recommend printing a stencil or just using a silver sharpie.
Step 3: Stamp it and Send it
Since I live with the person who got the San Francisco record I was able to get a picture of it. If I get pics from the others, I'll update with those as well.
UPDATE: all the records made the trip in one piece.