You can see that the reference model lacks your "CJA 1930" initials-date. Quick and dirty search engine results come up with Kennard's "Classical Junior Academy" for gifted students which was dedicated in 1930. See: http://www.kennardcja.com/index.php?p=2_2_History That is PURE conjecture on my part! It could be (and probably is) complete coincidence, but I thought it interesting especially in view of the fact that Laurens Hammond was quite gifted himself.
On 9/2/2012, one of these models (without the date/initials) sold on eBay for $76
Described as "Vintage Art Deco Hammond Gothic Mantle Shelf Clock Walnut Body Runs Perfect Mint" Item No. 251140271419
Here is one of the photos from the listing:
There was also one that sold 07/29/2012 for $39.95 on eBay which was not in running condition, also without the date/initials:
I'm sure you can find more examples online searching for "Hammond Gothic Clock".
I see they are listed as "Gothic B" on eBay.
Hopefully someone can help you with more definitive information on the date/initials.
Thank you very much for the detailed response! The first thing I thought of when I saw the initials was Junior Achievement, so it turns out I was close.
I keep hoping the prices will come up on these beautiful old electric clocks, they seem to be very under appreciated.