So a couple of years ago I had a parts-department sourced b18c5 block and head installed in the teg. A while ago I developed a leak in the head- dirty engine bay but no biggie. I've been having some cooling issues and was looking at where I need to replace the thermostat and noticed the round thing that junk yards put on engines. My question is- does the acura parts department put those things on new parts-department sourced heads or has my head been subsequently swapped out without my knowledge?

Also, can someone tell me how to read the date stamps on the head. They read:

(nothing/2) (nothing/6 or 9/nothing) (1/4) (9/0 or 0/6)

Thanks.