Bangor Punta owned O'DAY during the production of both boats (BP bought O'DAY in 1965 and sold the assets to Lear Siegler in around 1986). The so-called O'DAY 23-1 was built in the 1971-74 model years, perhaps 1970-75? The So-Called 23-2 was built from 1977-85. Primary differences are the early boat had a cast-iron keel with fiberglass centerboard, draft 2' bd/up, 5'5" bd/dn. !977-85 model had lead ballast contained within the fiberglass keel (molded as part of hull) and again, a fiberglass centerboard with draft of 2'3" bd/up and 5'4" bd/dn.
The 1970-2 models were offered in 2 versions, a pop-top and a fixed top, the pop-top was designed to allow the entire cabin trunk to be raised to allow standing headroom in the entire cabin (well exect the v-berth), this boat had the offset companionway. Disadvantage was that the cabin trunk slid up and down the mast as it was raised/lowered so the mast had to be keel-stepped and that made trailering harder. During the 1973 model year O'Day phased in a new pop-top version that I belive became the only version available on the 23-1 after that. on htis version only the part of the cabin top aft of the mast was raised, this allowed the mast to be deck-stepped in a tabernacle and was much less prone to leaks on a rainy day. This version still had the cast iron keel/fiberglass CB.
The later (1977-85) version was styled more like a smaller 25 and was never offered with a pop-top. I think a few of these might have been built with a fin-keel (like the tall-rig 25) in place of the K/CB, but I'm not sure. A few were also sold with factory installed OMC Zephyr 2-stroke inboards (15 hp sail-drive).