These were the Ericson 30 (MKI) - the first iteration produced from the middle 60s to about '69, and an early B. King design. I might be mistaken, but I believe the series was superceded by the venerable E29.
The raised cabin trunk was similar to the old Columbias, probably because escapees from Columbia Yachts were involved with founding Ericson. Or perhaps in the early days, elements of wooden boat building were still common in the CCA yachts.
Can't tell you how many were produced, but I've seen several still sailing after after all these years. They were heavily built cruiser-racers that shared heavy fiberglass layups common to other SoCal boats of the day.
Capt Dan G>E35II "Kunu"