Comics X-MEN original art - with question

[emblemcomics]

Hi guys,

I didn't locate an original art centric thread,
so I though I should start a new one.

I'm bringing this up, now with a proper link to the artwork,
because I really hope to get a conclusive answer to my "burning question":

Last week I finally got in my hands my very first Marvel piece -
Howard Porter & John Dell's cover to X-MEN UNLIMITED #18 (!):

http://qurls.com?i=46960

I was told elsewhere it's the only published X-MEN
(and Gambit) piece that Howard Porter had ever done.

This fact, had a bearing on the artwork's price (upwards).

I aware though that Howard Porter did two SOLDIER X covers,
so I'm not referring to these two (not to his Amalgam JLX one-shot).

I couldn't find a full guide which the trading cards artists,
so I couldn't be sure if he'd done any trading card art.
Nor did I find a guide to the in-house/commercial art/style guide pieces.

Please help me figure out is it's the only "proper" X-MEN related
art by Howard Porter. ANY info on the subject would be appreciated.

Thanks again,
Gal

P.S: comments are always welcome in my comic art gallery.