Exhibition 0 Reproducers

[Zeppy]

So I have (or rather Walt has) discovered something a little interesting about the Exhibition O reproducer. I've long had the Zonophone version of the reproducer kicking about, but a while back I finally grabbed a Victor one that was in horrible condition. Walt was kind enough to replate the Victor (as seen in its full glory below), but while buffing it, he noticed he wasn't finding the shiny glow of brass. The Victor Exhibition O is made of steel (tested by holding a magnet to it). To make thinks even more interesting, the Zonophone O is brass. Now my reproducer has a rather early serial number (2899), so I was wondering if all the Victor O are steel or did they eventually switch to brass?