I've seen him play a similar bass however I'm pretty sure this one is not his main one. Discuss. http://www.ebay.com/itm/1990s-ERNIE...S-/261248627143?pt=Guitar&hash=item3cd3a1b1c7
I don't believe this was his main bass as shown in youtube videos. Check out the kahler tremolo bridge. Not as advertised in the ebay ad.
On the Autograph I got from him in the mid 90's he only signed "Mark" with the smiley. Plus his main MM style bass during the late 90's period was an Ibanez ATK. C/S, Rev J
Haven't seen him or been down to Rockin Robin in Houston lately but I usually saw Mark playing a MM covered in stickers. I think it was the same color scheme though. I saw a documentary on The Wetlands that contained some of the Spin Doctors history and had live footage that may help.