In terms of main bracing for the instruments these are the three most common types that are used on the majority of the instruments. You can clearly see this on the image below which runs from the 1920's into the 1950's. The 3 models with the largest variation were 1) Martin Handcraft Imperial with the Art-Deco angled braces. These braces are well defined and extremely rigid. 2) Martin Handcraft Committee: which used the post style braces 3) Martin Committee which was extremely light weight and probably quite easy to make as they are just the same material as the band lyres bend into shape and soldered.