The difference in a model 1 and a #5 fighter is the five is not dished out on the spine just forward of the hilt. With a 5 fighter you actually lose some of the functionality of Lt. Zacharias' fighting grip. However, ( and I'm sure the Cap'n or someone will correct me if I'm wrong) a 5-5 can be had with sawteeth, a 1-5 no longer can.
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Wally