I have a inkling that the HQ Sandman was to be a limited build initially, much like the VSIII SS ute. So GMH built a quantity for sale early on in 1974. I think this is where the numbers that get thrown up from time to time come from i.e. this quantity was a distinct number like 100 or 200 or whatever. After they sold quickly then you could order them and more were built for stock order.