Piston oversizes oddity

[jp928]

Have a spare NA8 engine (94 by the look of it) I am starting a rebuild on - suspect it is a grey import. Removed head and sentn out for clean up. On cleaning the piston crowns, I find what looks like oversize markings....3 are stamped '25', but cyl 3 is stamped '19'. '25' I understand would mean .25mm over std, or 0.010" over, but '19' ?
Any suggestions please? The bores all look very good - hone marks visible all over, no lip detectable at the top, most of the crowns rubbed pretty with metho, doesnt look like its led a hard life.

thanks
jp 92 NA6 96 NA8 turbo

[noobee]

measure them?
With regular oil changes BP engines are said to wear very well.the one I rebuilt for my son (had maybe 90k on it) mostly measured up within new tolerances.It was a shame to pull it apart,lol.
We had to beef it up a bit internally for more power was the only reason.
Mick

[jp928]

I only have a digital caliper, and I can barely get that to read higher than 82.9mm, where nominal is 83.0mm. Dont want to spring for a good internal mic, so will probably have to take it to a pro to check.

jp