Hasselblad E16 Back on 501C body?

This is a two part question.

What does the E stand for on the Hasselblad E16 film back?

Second question is will it work on a 501C body?

The E back has electronic bus contacts to transmit ISO information to the 200 series cameras.

They work fine on a 501c.

Absolutely. The E-magazines are generally newer and therefore likely to be in better condition than most A12.

For some reason, the E12 seem cheaper on the used market than the (newer-style with slide holder) A12N... Not sure whether this also applies to the E16.
I personally use a couple E12 I got for a good price. Never had an issue.

EDIT: just had a look at E16 and A16 prices on that famous auction site... price seem through the roof. Crazy. I think that shooting regular 6x6 and cutting away 1/3 of the roll whenever 645 format is desired definitely costs less.