Unidentified Stuart vertical

Incomplete vertical engine, looks to be of some antiquity from condition of the paint. I'm sure it's a Stuart, I'm not sure which one. One of the site's resident Stuart experts will, no doubt, come to my aid!

Comprises base, soleplate, column, complete cylinder/valve chest assembly with piston and valve, draincocks. Crank and flywheel, connecting rod and valve rod. Missing main bearing caps, crosshead and support rod.

Height 8 inches
Flywheel 3 1/2 inch diameter