Hi Joe,
the "To John Harrison" reference 49910 comes with basically the same manufacture made movement caliber GP 33 RO as the 49900 "Sea Hawk II". Just that it sports a small second.
I?m sure there?s no breakup of production totals for the variants; the ref. 49910 is a current production model and thus they are still being produced.
There is a number of different dials; basically the dials available match the dial colours for the Sea Hawk II and include glossy black, blue, ruthenium grey, white and the "waffle" dial with hobnail patterns:

