[darwinbulldog]

The usual Henry Johnson stamp reads as follows:

Henry A. Johnson,
Wholesale Confectioner,
1827 Bay St., Alameda
Phone Alameda 2785 W.

The other stamp replicates this format from everything we can see. Here's what I can make out and, in bold, what I have extrapolated to be the most likely missing text (after more time and effort than I would care to admit but which will become apparent if you continue reading on for some reason).

Howard P. Boyer,
Wholesale Candy,
??2 Thirty-Ninth St., Piedmont
Phone Piedmont 6149 W.

If each line is centered, there are three missing characters after the "BO," which gives this list of reasonable surnames, in order of descending frequency in the U.S. census:

Bowen
Boone
Booth
Boyer
Boyle
Boggs
Boyce
Bower
Bonds

When you search for each of these names, the only one that returns a clean result from Google is a current listing for a Howard P. Boyer who lives in Sacramento (i.e., also in Northern California, like the confectionery companies). Maybe that doesn't mean much, but it's enough for me to guess that Boyer is at least slightly more likely than any one of the other names on the list. The others are certainly possible, but Howard P. Boyer is my educated guess/working title for the type card type.

39th Street in Piedmont is quite short compared to most of the other numbered streets and seems always to have been this way from old maps of the area. It only runs up to about 1100, so the address here probably had only 3 digits.

The word Piedmont at the end of the line is assumed based on 1) amount of missing text we can extrapolate from the centering and 2) the format of the Henry Johnson stamp.

The placement of the presumptive P in Phone on the bottom line neatly lines up below the W in Wholesale, and the 9 in the address ends below a spot between the presumptive D and Y in Candy, leaving one missing character which should be either an E or a W (N and S are less likely but possible) to fall below the presumed comma. I don't know how their telephone exchange listings worked in the 1920s, but if you look at a map (or many maps as I have now), you'll see both that the Henry Johnson address is in fact located on the western half of the town of Alameda (distinct from the town of Alameda Island which actually occupies the same island) and that the entirety of 39th Street is on the western outskirts of Piedmont, so I'm guessing the missing character is a W.

And if anybody ever finds another one of these stamps we can see if I earned a passing grade for the detective work.