Well, not exactly germane to the OP's question, but if he goes to sell it the question will arise, "What do I call it?"
Where is the dividing line between the New Wonder II and the Artist baritones? For alto and tenor there were any number of major acoustical and mechanical changes. I've never seen anyone claim that similar changes were applied to the baritone. When it was New Wonder:
- they didn't stamp the stock number "12M" near the SN
- the bell keys were on opposite sides
- the high E touch was flat
- and it had New Wonder type engraving on the bell
When it was Artist:
- they stamped the stock number "12M"
- they moved the low B key around, by a simple linkage
- They made the high E touch curved
- and it had the "lady face" engraving.
As far as I'm concerned, none of these really rises to the level of "new model". They're all either simple appearance things, or minor mechanical changes.
There were thousands of Artist 12Ms made before the front F key was added, so that's not an indicator.
What the OP has is with both bell keys on one side and curved high E. I don't know if the letters "12M" are stamped above the SN (but it was still the Conn internal stock number for "Eb baritone sax, low pitch". I can't tell what the engraving looks like.
To use the popular parlance, I'd not call this "transitional" I'd call it a "12M" or "Artist" model. Other than possibly one small stamping and possibly some bell engraving, it looks exactly like what we now call a "12M" baritone.