Bart, mine is 76-73 so was built in 73 and would assume it was sequenced as number 76 of a batch.
Just to revisit the recent subject of IFR, whilst reviewing my original factory application for certification (from the disc faa records will sell you), I see in section III. C. "Aircraft Operation and Maintenence Records" the box titled "Check If Records in Compliance with FAR 91.173, is checked. Interesting, no?
Further, Note 1. of the TCDS says current W&B report together with list of equipment included in certificated empty weight must be provided at time of original certification. No mention of continuing to carry it. Shame that all docs were not submitted and copied originally as they are these days.