R class spare wheel size?

[97 SL320]

Any year R class, does anyone know the width of the spare wheel? Near as I can tell the part # is A 251 400 00 02 . Various searches come up with 6.5" and 8" width and 18" diameter.

So far is looks like inflatable spare tires were standard, ( the inflatable / collapsible spare dates back to the 70's pioneered by BF Goodrich )

Also, did the R class come with regular use steel wheels outside the US? one search comes up with Transwheel brand PN STL65395U45 18 * 8 but they are not in stock or likely to be in stock.

Thanks

[97 SL320]

Update, got a hold of a R class spare.

The wheel is stamped 251 400 00 02 6.5 x 18 40 ET