Heres a copy paste of the same thing my car has that I found on another forum:
Re: K-frame coins
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Reply #18 on: May 21, 2009 - 07:30:38 am »
Quote from: Alaskan_TA on May 20, 2009 - 11:37:11 pm
52 is correct for T/As, AARs & 318, 340 & 383 cars after about mid-1970 model year. The 52 is on the broadcast sheets, it is the last two digits of the actual part number.
Date codes for these are stamped into the flat vertical surface on the front of the K member.
That would jive with why my car has a 72 not a 52 - it was delivered in April 1970 so would have been manufactured before the mid-1970 model year.
Like said before, not here to argue, just something i found interesting and would like to understand the change. Also helps with documenting the car.