Fords prefix is good but I've always liked Harley Davidsons suffix. after the Part # there is a dash XX and what ever the number is the year it was first used. My 91 has parts that were first made as early as 72.
All these #'s are good to know..

56 Vic, B'Ville 200 MPH Club Member, So Cal.

According to my Parts Catalog 52 and 53 Ford Passenger Car with standard Heater use the same Switch.

  

Thanks, Hoosier Hurricane.  I have three separate 1954 Mercury shop manuals, repair and parts, and one covers '53-'54 and another '54-55.  I had guessed the prefix was for '53 but wanted to be sure before making it available for sale.

The B3AZ prefix indicates '53 Ford passenger car.  That doesn't mean it doesn't fit other years and models though.

John - "The Hoosier Hurricane"

I have among my hundreds of '54 Merc spare parts a NOS blower/fan switch, part # B3AZ-18578-A.  The part number indicating fitment for a 1954 is FDC 18578 B and I am wondering if any of you Y-Blockers can decode the prefix (B3AZ) as to year specific for this switch.  It is possible that it fits '49 - '53 which obviously would not be in the Y-Block era, but some of us straddle the line with the flatties.

Any help out there?