That's a nice PC59-771 (77+P15) Don!
Someone could make a nice specialty collection just putting together a die state set of P15 reverses. I believe it has more die cracks in it's last state than any other 1859 N9 reverse. Yours is a late enough die state to also have the heavy obverse 77 die crack at the back of the R of REGINA.
After the P15 reverse die was retired, the obverse 77 die was paired with the P15a reverse die for a short time. Then obverse 77 was retired also and replaced with obverse 77a. Obverse 77a was paired with 4 reverses and none of them lasted very long.
The whole grouping from 771 to 77a4 (6 die pairs) is interesting to collect and study if you like die cracks.