Only 23 Panthers produced with all steel wheels chassis numbers 121032 - 121055 first produced on or around the 22nd of september 1944. zimmerit was stopped being applied on the 9th of september 1944.
In March/april of 1945 M.A.N produced several Panthers with a steel wheel on the last station, its not known whether this was a shortage of rubber or an attempt to reduce roadwheel failure.
Panther steel wheels were the same as those fitted to Tiger 1 and 2 except for the hub.(source panzer tracts no 5-3 Panther G by Jentz and Doyle)
I have never seen a picture of a steel wheel panther with a Chin mantlet though (waiting to be proved wrong now

)
BTW panther looks great Iain
Cheers Ian