Hello Jay
Well don't count on that. Remember Vapor's hull construction was very different from the Herreshoff drawing. Carvel planked and fastened with nails and roves. Not double planked and screwed as you would expect.
In Vapor's Triple engine the low pressure piston had a piston ring. On the drawing there is no piston ring and the piston is very light. There are no amendments on the drawing showing a ring at a later date. Vapors engine could have been rebuilt by others just like the hull. Interesting to me. The piston valves on my replica have no rings. On the MIT engine there are rings. The Hp and IP pistons on my engine do have rings similar detail to the MIT engine. HMCo seemed to do drawing of every thing they made and changes were recorded. Thanks to MIT Museum we are still using them today.
Regarding the lack of piston rings, I guess, the designer figured the steam pressure drop due to slippage past the pistons was minimal and compensated by the lack of friction had there been piston rings. Some one may have a better answer??
Chris