I have, what I believe is, a Herters shell holder. It definitely does NOT fit an RCBS. It has a 3 stamped on it and according to a chart it fits a 30/40 Krag and also 303 British. There may be others that it fits, but I have confirmed the 303 British.
I am unable to up pix, so PM me and I can text them to you. If you have any questions or need dimensions, let me know.
Price: $15 shipped