Actually, i've never seen one in bronze green. I do have some early pictures of series 2 gunbuggies, and not one in deep bronze olive.
THe gubuggies were converted from existing general service and forward area ambulance vehicles. As far as I can tell they were repainted as part of the conversion. Either to a olive drab, or a pale brown. Because they were front line vehicles they got the better camouflage sooner. for the same reason the gunbuggies were some of the first to get camouflage schemes as well.
Actually, to be honest we aren't sure exactly when the gunbuggies were converted, it appears to have been around the time of the colour switch.
here is an early pic of a series 2 gunbuggy (as opposed to a 2a) from ANZAC steel.
and an earlier B&W one, doesn't look like gloss to me.
here is the page on REMLR about the gunbuggies.
http://www.remlr.com/2_2Agunbuggy.html
another pic which looks like an early PR photo and may be in gloss bronze olive, but it wouldn't have been for long.
this page of pics is of dinty's series 2a gunbuggy.
http://www.remlr.com/dmshedtopless.html