DO a show ver and look at the IOS loaded.
For example
System image file is "slot0:c5rsm-isv-mz.120-20.bin"
The "isv-mz" tells you what it is. There is a table some where that tells you what the family is. There is a whole Cisco press book on this subject!
Here are some that I know:
js= enterprise
ds= desktop
is= IP only
