These are early wet process power pieces, U-935B on the left and U-935A on the right. The grooved version, U-935A,which is a copy of the GE dry process, has a date stamp of 3-12-97 and the U-935B, has a date stamp of 3-16-97. With only four days between their production, I can't help but wonder if the top of the U935A was just too difficult to manufacture, resulting in the simplified crown of the B version. See second photo for a view of the tops.