Rhodes 19 and Mariner might be same, but
The Mariner and Rhodes 19 may be similar (I think jib sheets were different?), but the comment made was that the Mariner was different from the O'Day 19. The O'Day 19 WAS a different boat and was rigged quite differently from the Mariner. O'Day has built 4 different 19' boats over the years, the Rhodes 19, Mariner, O'Day 19 and O'Day 192. The Rhodes and the Mariner are basically the same (same hull, different deck and slightly different sail plan). The O'Day 19 was built from 1979 to 1984 and was introduced the year after O'Day stopped building the Mariner. The 192 was a smaller version of the 222, and was introduced in 1985. The Mariners built after 1974 (change was actually made partway through 1974 model year) have a different mainsheet. The sheet is located at mid-boom, there is a block with becket hanging from the boom and a double block (actually a fiddle-block) located at the aft end of the centerboard trunk. The mainsheet is spliced to the becket on the boom block, runs down through the upper sheave on the fiddle-block, back up and through the block on the boom, then down through the lower sheave on the fiddle-block and through a camcleat on the block.
