We are on a statewide adoption of the ICODES, currently under 2009. I have, for our jurisdiction, by policy, incorporated the 1997 UMC Clearance reduction tables for "Unlisted Appliances".
The reason for that, is the current codes specify that "all appliances shall be listed and labeled."
State of Washington has an amendment allowing historic or antique cookstoves (mfg. prior to 1940) to be installed, however no provisions are given for clearances and from that era, they are unlisted.
The 1997 UMC seemed to solve this.