I think that the box was incorectly labeled & I think that it's a console mount clock for the 1200.
It will work in a dash mounting too I believe, but the welded-on mounting lug isn't used, only when console mounted.

I certainly hope it's a 1200 clock as I bought one also. The lovely bright dayglo orange on the second hand is all faded in mine, so a new clock will perk up the interior just nicely.

120Y clocks are smaller & square or rectangular & you shouldn't have too much trouble selling it as these seem to be in demand.