Did several searches, but couldn't find an answer to this question. I'm doing a clutch install and had planned on resurfacing and reusing the stock flywheel. I got the flywheel off tonight and planned on dropping it at the machine shop tomorrow, but I noticed a four digit number engraved on the back side of the flywheel. Has anyone noticed this on a stock flywheel or can assume this flywheel has been out and possibly surfaced once before. Thanks for any info.