Yes, absolutely, and noticed that Maurice P. Burke identified aluminum as the intended casting material for all metal components for that patent. Since he also hinted at "or some other similar material" in the same sentence, I still plan on doing the specific gravity test and recording the results. It might prove useful to know down the road as we attempt to pinpoint Burke production variances and dates. I don't know of any way to learn the date of manufacture on a Burke chair at this time.
Also, I didn't know that about the Burke 115 to 116 assembly interchangeability. This is great to know and appreciate you confirming this as well as in clarifying the proprietary nature of the other type of memory return and its propeller. I'd still want to learn how this different memory return setup in the picture works and try get a rough idea of how often you run across those because I think it's going to be a hit and miss proposition. Sellers either don't know or don't like to publish the most primitive description about these chairs in their listings and a lot of the time won't answer the slightest of questions posed.
Of the three Burke 116s I've run across, the memory return mechanisms were pretty much the same -- the only difference being some extra support webs that were noticed in the casting on one of the memory return mechanism housings. The hardware that affixes the memory return housing to the propeller castings were all the same. The receiving thread holes all aligned between them and were of the same thread size and pitch.
I was going to paint a couple of Burke 116s this week but there was a weather delay. Given that uncontrollable variable I'm thinking the best thing to do is to wait for the 115s to arrive and then just paint all four chairs at the same time. That way, I only have to clean out the spray gun one time and put things up only once.
Based on my own experience, I'll wind up getting the Burke 115 chairs in next week and the propeller heights won't match the listing photos or some other work stoppage level issue... Sooner or later, I'm going to setup an aluminum casting capability of my own using a mold and some sodium silicate.