If you've got a vintage Iron Man comic tucked away, my heart races just thinking about it — those old Marvel books can surprise you. The tricky part is that "first issue" can mean different things: collectors usually mean either '
tales of suspense' #39 (1963), which is Iron Man's first appearance, or the first solo series issue, 'The
Invincible Iron Man' #1 (1968). Values swing wildly depending on which book it is, the page quality, restoration, and especially the grade given by a service like CGC.
For a quick ballpark: a high-grade 'Tales of Suspense' #39 can land in the high four- to six-figure range if it's near mint; mid-grade copies are typically thousands to tens of thousands; worn copies might be in the low hundreds to a few thousand. 'The Invincible Iron Man' #1 is valuable too but generally less astronomical — think high-grade copies in the low five-figure range, mid-grades in the low thousands, and beat-up copies for under a few hundred. Signed copies, variants, and paper quality (white vs. off-white) all change the math.
If you're curious about a specific value, I'd get it professionally graded, check recent auction results on sites like Heritage and eBay sold listings, and compare GoCollect or GPAnalysis trends. I always get a little giddy seeing a long-neglected comic climb in value, so good luck — hope your copy turns out to be a keeper!