Hi again,
A little more research indicates that the early version of this plane was referred to as a four square jack plane, before the 5 1/4 number designation was assigned to Stanley planes of this size. Another common term used is “junior jack). There have been several of these that have gone through EBay that sold in the $35-$50 range but I do hope you will tune this one and put it to work at your bench.
Have fun