I have this exact same bike from my grandfather. I tried to check the cranks for any markings, they are marked Sugino Proto Japan but there is no date code or markings on it. I can see it was made in Canada as well.

I am really interested in the year of this machine. There is nothing special about it other then sentimental value, he etched his full name in the top tube in case it took legs at the post office I suppose...

I cleaned, inspected and repacked the headset & bottom bracket and through a flip flop set of wheels on it as it has horizontal-ish dropouts. I will continue to ride it for years to come. I kept all the original bits should I want to revert.

Does anyone have any info on this bike?