Hi kbu,
I'm not sure there is a "correct" place, but I put my serial numbers at $FDF0
This is the top 16 bytes of the second last page.
This way I'm very high and out of the way, but not so high as to be in the vector/non-volatile register page.
Seems as good a place as any to me.
BTW, you only need to dedicate a whole page if you are likely to want to change them with out re-loading all the code (or the rest of the page).
Regards
Peg