[Closed] Which diameter aheadset bearings?

Hi folks

I've got a problem with the bearings on my road bike headset. I've stripped it down and the bearings are buggered but I've got no idea of the diameter I need to spec for the replacements. They sit in a wee metal 'retainer' and there are (or were until 10 minutes ago....) 26 of them there. Any ideas how I can check it out? It's an old unbranded headset so I can't track it down by manufacturer.

Cheers
TS

PS I don't have anything I can measure them with accurately.

PPS The bearing retainers have an outside diameter of 38mm.