It was not uncommon for Greg to make non-catalog sheath styles for RMK's...ESPECIALLY before the fire and Greg's nearing retirement era. The "Tampa-Oval" stamp was used a good, long time, even after the shop had moved to Odessa. Shortly after the move, new leather stamps were made, indicating the new location.
Danny Gutcher may add more to this but it simply looks as though a customer "special-ordered" it from Greg...in the old shop.
Hope this helps, Capt. Chris