Hello all, I protray a Musician in the Engineer Brigade Band as well as the principal musician for the Co. A re-enacting unit. I can say pretty decisively that the castles on straps are a reenactorism as with many things we know. While other services call for letters or insignia of a sort to be displayed in the center of the strap, but neither the horizontal nor vertical engineers call for it by regulation. I have yet to run across any images or surviving originals of castles on straps-can I prove a set never existed, of course not, but the evidence shows not thus far. As stated, the topographical engineers were a very elite and proud corps, and as a consensus did not like their integration with the “ Lesser corps” as one officer put it, when they became one branch in 1863. Officers of this corps commonly retained insignia and openly defied the 61 regulations for them on their straps and hat devices.
May I ask which belt buckles you are using for your drawings? This is an equally if not trickier detail to nail and I’ve done a fair bit of research on it and am happy to share.