No other guesses? Oh well, it is pretty esoteric.
FE and FC vans and utes assembled at Melbourne and Perth had the external mirror factory fitted, due to local regulations. The guard-mounted job is the cheapest of the wing-mirrors (by about 2 shillings), so that's the one Holden used to meet this requirement.
You almost never see that mirror elsewhere, as it is a right mongrel to fit, and not even as effective as the door-mounted job.
All the Nasco mirrors can be seen in the
Trim and Style Accessories section of Tech Info.
cheers
RET