Timbo,
I had a look at the stops and they're the nylon - pop rivetted style. I'll get some newies and in another 15,000kms put 215mm tyres on rather than the big 225mm ones. We are in our 50's and 60's d and don't need 9" of rubber on the road anymore. 8 5/8" will suffice.
By the way, the 18's we have are pretty scraped ( I think in the decade or so the car was stored, the wheels were swapped).