Correct officer's US collar brass and branch insignia for pre-WW2 uniform

[oakleaf777]

I recently bought a pre-WW2 US Army M1926 pattern officer's tunic. It has all the insignia removed, and I'd like to add period correct rank, US collar devices, and branch insignia. From what I gather from some preliminary internet research, the collar devices should have screw post with clutch attachments, while the rank should be pinback attachment. Can the collar insignia be pinback as well? Since the screw post insignia look like they would make pretty big holes in the uniform, I would like to use pinback insignia if they would be period correct. Thanks for any advice

[KurtA]

It is quite common for collar insignia of that period to be pin back.