Dave, it might not be stainless, but it's a brushed silver color and is definitely steel. It measures 0.75 OD and the height is 0.705 of and inch. I think it is the drop through bushing as the machine is set up for 45 ACP currently and I do have a 38 tool head and set up parts for it.
Regarding the brass bushing, I was also thinking it could be a case guide for 38 Special brass, as 45 brass will not fit through it but 38 will with some room to spare.
Thank you for the help!