Here is a rare Cantu stamp that isn’t from the 1987-88 swarm, on the east side of South Clemens Avenue between Prospect and Kalamazoo. This one is just Cantu and Son. Evidently only one son had thus far joined the business.

It is difficult to read the date, and the photo doesn’t do much to make it clearer, but close inspection leads me to be pretty sure it is 1980.