All the blue 'JD Suspension Discs' I have seen close up down here in New Zealand have all got the transfer printed words:

Pat Feb 3, 1920, Mfg, AUG, 1927.

The month will vary as I have got ones with May, Jun, Jul, as well.

This post is should have been added at same time as the other ones I posted a while back. I am doing so now as I was prompted by an ICON request for dated 1927 insulators.