The pics above should make idenifing the difference between the two without a doubt, but one more way makes it easy also... Look at the side area where the halfshaft inserts into the diff, the R-180 will have a bolt on cover (oil seal area) with 6 or 8 bolts.
The R-200 will never have this. If you look at each halfshaft, toward the diff, and see bolts on the diff itself, (not the halfshaft) its not a R-200... 8)