Jointer plane: Stanley? Gage?

What can you tell me about this plane?

This is what I know about it:

It is 21" in length, 2-5/8" wide, and the iron is 2-1/4" wide. the side profile looks like a Gage plane. The iron is stamped with the second Stanley logo, which came directly after the the logo that included the patent date Dec 25, 1867--so this iron was first introduced in 1872, and was superseded prior to 1890 as I recall.

The only other marking is a faint 6 7 on the underside of the lever cap.

Here is what is unique about it: the brass depth adjustment knob is not centered--it is offset to the right. I have never seen this type of frog/adjustment mechanism.

I cannot find any info online about it. I have Alvin Sellins Stanley book--the only thing close are Gage planes that have the same side profile, but the lengths, and frogs/adjuster/blade are all different. Stanley Gage planes seem to only date back to the 40s.

Any insight to the history of this plane would be greatly appreciated!