Jahns 401 Pistons - UPDATED with Specifications and Pictures

A0M797X112187

Out of sheer luck, I recently acquired a new old stock set of Jahns F-1181RP forged flat top pistons ( 0.030" oversize ) for a 401. Does anyone know the technical details of these pistons ? Being flat tops with 2 valve reliefs, I am guessing that the compression is probably 12:1 or more. Do they have any collectors value ?

A0M797X112187

OK, it took me a while to get around to this but here are some pictures and numbers for the Jahns pistons I have :

Pin diameter : 1.000", pin tapers inward on the inside.
Compression height : 1.510" as measured with my Mitutoyo 6" caliper. 1.510" NOT 1.501".
Ring grooves : 5/64" / 5/64" / 3/16"

Pin bores are grooved for the spirolocks and the one piston I unwrapped for the pictures weighs 745g according to my super high-tech scientific Wal-Mart digital kitchen scale 🙂

The gap where the small end of the rod goes is 1.368" wide if that matters.....

The IMPORTANT envelope has some general information as far as fit is concerned but no technical details about these specific pistons.

Again, any insight or knowledge about these would be greatly appreciated !

Thanks !