Mark II was introduced with the '87 Model Year
The 'T' Shaped cockpit, Universal M-25XP, the forward facing nav station and standard wheel steering were introduced with the 1987 model year (produced starting in late 86). In addition, the cabin top traveler was changed from an arched abortion to a flat track. This also made the companionway slightly narrower at the top than with previous years. The pushpit rail was split into two halves with a walk through area for the aft boarding ladderSome time in 1990 = 1991, a few Mark IIs were produced with a walk-through transom. These boats still had the narrow stern, but the aft lazarette was split into twp parts, and a gap was cut into the center of the transom to enable people to walk through.In 1993, the Mark III was introduced with a much broader transom than either the Mark I or the Mark II models. You will make no mistake identifying a Mark III. It has a purpose built walk-through transom with a boarding area and a step up into the cockpit. The stern boarding ladder mounts to this scoop. About this time, the wing keel was also introduced. Although there may be some late Mark IIs with wing keels, this option didn't appear until after 1990, and I don't think that it was available until the Mark IIIs. The primary differences between the Mark III and the Mark II are the width of the stern (the Mark III has a real wide rear-end) and the fairly well designed and executed walk-through transom. You can't go too wrong with either a Mark II or a Mark III.Good luck