[JerseyHighlander]

Every photocopy of Long Form BCs from that hospital from that time period that I have seen have a similar disappearing digit, it’s from a rotating date rubber stamp for the date and a rotating number rubber stamp for the ‘File Number’...

here is modern equivalents for rubber stamps:
http://www.rubberstamps.net/date-number-stamps.aspx

[grundle]

Thanks for explaining that.