Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

Interesting YouTube I found about the difference between the B-38 & B-40 Engines.  This fellow seems to explain that when Empire sent out the B-40 (which comes with the B-40 display) for dealers/stores people wanted the B-40 Hot Air Engine for themselves.  So Empire released the B-38 for people to buy - which makes total sense.

YouTube link to Empire model B-38 hot air (Stirling) engine