Thats a good question. Most of the enfield bayonets circulating here are imports and were not used in the American CW. I suggest you take a look at period photos and try to figure it out. There are lots of them at http://memory.loc.gov/ammem/cwphtml/cwphome.html

Download the archival tiff version and you can use your photo program to zoom in on whatever portion of the picture you want. Hard part will be to find some troops with enfield muskets.