There were six distinct groups of 80' ELCOs completed during WWII and, while outwardly similar, they displayed some major differences. I've drawn the lead boats of the first three groups and will eventually cover all six. The groups encompassed: first (PT103-196); second (PT314-367); third (372-383); fourth (PT486-563); fifth (PT565-624); sixth (PT731-760). The 731-760 boats were built expressly for the Soviets. Only the lead boat (PT731) was actually built at ELCO, the remainder being shipped as "kits" for the Soviets to assemble. A seventh group (PT761-790) was planned and a few actually started, but none were completed. This last group was radically different from the others and will make an interesting study.