I suppose maybe looking at features vs dates of parts books and/or WD? I’ve tried to put multiple issues of the parts books on line. 
https://www.navy-radio.com/manuals-ttycorp.htm
Let me know if you are looking for a particular issue that I haven’t scanned yet. 

Also see Mark 1,2,3 differences…
https://www.navy-radio.com/tty/28-mark.htm

Don’t know of any serial number vs date info. 

Nick England K4NYW
www.navy-radio.com


On Mon, Dec 18, 2023 at 4:41 PM B. Smith <smithab11@comcast.net> wrote:
Is there a method to determine the date of manufacture of a Model 28?
k4che

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