[GreenKeys] M15 Typing unit U.S. Patents

[Normand Marks]

HI

I have a curiosity question, and it is with the "GreenKeyers" that have
M15's, what is the starting U.S. patent on your typing unit?  I have two
units listed below.

 

TTY1 starts at 1370669 ends at 2257553

TTY2      "       1719489      "      2257553 (UPS sign on cabinet)

 

Which machine would be the oldest?

 

Thanks

Norm

WB7WEQ

 

 

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