unfamiliar with that shape as civil war related.however freemasons used that shape commonly.appears to be missing inlay.trouble is also there are a dozen countries that use the maltese
cross shape for military badges and medals.templars too.
Without the center piece it'll be impossible to positively ID it. Medals like that were made for everything from veterans groups and fraternal organizations all the way to school bands. Search "maltese cross medal" and you'll find hundreds of images, you may be able to track one down with a matching design.