Bolt marking question

[chopperbobby]

Was filling out m1 carbine data sheet today. Looking at the bolt it is a Winchester round. W on right lug (no hole on bottom). The question is on the bottom of the lug with the W is a 5 stamped? Can’t dind anything on this. Any insight would be appreciated. Thanks in advance

Information

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[new2brass]

Marks have been reported in i believe starting 5 million range.
I beliebve the Carbine Club Newsletter on 5 mil block which mentions it

[new2brass]

Just had time to check, 5 Mil block update does not specifically mention the numbers. 6 and 7 million update does mention it and believed to be inspection marks.

[chopperbobby]

Thanks. Mine is a mix master Winchester 5750000 range