The changes is subtle but here are the changes between the dials:
The "E"s in "DEEPSEA" now have a shorter middle line.
The "S" in "SEA-DWELLER and DEEPSEA" has been changed from a "flat" tail to a "rounded" one.
The "ft" font has been changed.
The "=" sign font is no longer Italic.
Larger gap between the ft and metres depth rating.
Pictures below borrowed from the Internet.
MK. 2 dial

Mk. 1 dial
