Can someone help me out with what model this is ?

i found this at an estate sale - the back says "10k rolled gold plate bulova L6" and "b084757" there is an engraving reading "FBI Detroit R.W.R 10-12-56" i did some research on here the L6 means it was made in 1956 but i have no idea as to what model or anything it is. Any help would be appreciated ... and where could i get a nice authentic band for it thanks

                                           Jacob