Paul, some examples of details that maybe your contact can describe:
1. Are the grooves on the tailplate cap cut with a slight spiral or are they cut at right angles to the cap rim?

early JVH

2. There's too much grease in your photo for me to see if the pinion (arrow 1) has a square hole or a round hole with a key groove. And is the pinion steel?

Some folks did not mount pinions on squared spool shafts.

3. What is that thing under the brake spring indicated by arrow 2 in your photo?
4. Is the crossbridge of the foot flat or concave? Is the foot a one-piece casting?
5. Does the part numbering with Arabic numbers, including the "25" scratched on the headcap suggest American, rather than British, manufacture?