Unknown IV badge

[lettman]

Any thoughts regarding this recent acquisition? I assume it's a Roman numeral 4 rather than the initials I-V, and it's approximately 27mm wide by 18mm high. I'm aware that the 4th South African Armoured Car Regt and the 4th Gurkhas wore a Roman numeral at some stage, but my sources show theirs having a local manufactured look, while my example seems a bit too 'ordnance'. Thanks in advance for any information.