When you lay them all out, ready for painting, 622 incorporates quite a few subassemblies! Thirty-seven, in this photo, but I’ve left out the cab windows, so that’s another seven. Forty-four subassemblies in total.
While I had all the subassemblies in one place, I also took a few minutes to count all the parts. 513. That may sound a lot, but #10 incorporated 1162 parts. 3D printing, etching, die cutting and casting saved me from fabricating over 50% of the parts. What’s more, I feel there’s room for further simplification: I got lazy toward the end of drawing, and left some things to be modelled later. Perhaps the next engines will be closer to 400 parts.
Pembroke:87 
Do you maintain a spreadsheet to track parts? It makes perfect sense and my question probably sounds silly. It’s neat to think that the experience of building these engines translates into ideas on how to streamline your their production.
Spreadsheet? Good gracious, no! I simply go over the model and recall how I made each piece. Truth be told, the number is probably a little lower than actual as a result, but very close.