what model(s) are you inquiring about. I have been researching the 2270 only for 7 years. Info has been posted on here for awhile. I still update my information and post from time to time.
It would be good if maybe you did not duplicate my work already done.
As a suggestion many owners do not know difference between silver and champagne engraved units which can really mess up research. I always ask for photo of face plate to verify.