[Ron Ramirez]

The thing is, Philco of Canada did not start using a "3" in front of their model numbers until 1933.

And the listing of Canadian Philco sets on my site, which was derived from Philco (Canada) factory info, does not include a 370 Lazyboy chairside which would seem to indicate that the 370 Lazyboy was not built or sold in Canada.

One more thing. While it appears that many of the Canadian-built Philco sets were made for 25 cycle AC, not all were. Yours is an example (40 to 60 cycle AC). A Model 70 set designed for 25 to 40 cycle AC would be a 70-A.

But none of this really answers your main question - the "3" in your set's model number tag. My best answer - I don't know. I do feel that the added "3" is suspect since it is stamped deeper and is of a different font, so was obviously added after the original stamping was made.