The MobiPerl command mobi2mobi will print out the clipping limit, but in Hex. For example I saw 0xa (10), 0x1e (30) and 0x64 (100) in three AZWs. You can use Google to convert: search for "0x1e to decimal". Note that this limit can be in DRM-free AZWs from the Kindle Store (which all seem to have a limit of 100), but isn't usually in DRM-free MOBIs from other places.
If you use mobidedrm to strip the DRM, the clipping limit is still there. If you then run the MOBI through Calibre, it is no longer there but I don't know for sure that this means there is no limit.