This particular 4-gallon pressure tank was made between 1954 and 1956. After looking closely at the pictures, yours is the 1954 model of the Evinrude Cruis-A-Day tank which is distinguished by the bolt on lobes and the threaded connection barbs.
The 1954 model also has a third round hole in the diaphragm that corresponds to a walled off chamber in the upper housing. In subsequent years, the outer wall of that chamber was removed, and the chamber is actually open to the rest of the tank. The third round hole was no longer needed, and probably never was needed.
The newer/old style 1955 and 1956 diaphragm with just two round holes, and nine small holes will work fine for this rebuild.
Here’s a picture of the later model upper housing where the chamber wall is removed. This is a 1957 or later tank with the plastic push button.
Here’s your 1954 upper housing with the closed chamber:
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