For those of us who can't remember 1971, it might be difficult to explain why an automaker would walk away from muscle cars, especially one as dominant in its heyday as the Plymouth Hemi Cuda. By then, muscle cars felt played out; between smog laws, gas prices and rising insurance rates, power stopped being quite so cool. Those trends were temporary, but they still reverberate today with the reverse effect — making this 1971 Hemi Cuda convertible potentially the most valuable muscle car ever when it goes up for sale next month.

The last of the fire-breathing Barracuda variants have always been sought after; because of waning demand, Chrysler made only 11 Hemi Cuda convertibles in 1971, each with the 425-hp big-block V-8 and numerous optional go-fast parts. Another '71 Cuda was the first American muscle car to sell for more than $1 million in 2002, and a white convertible with an automatic transmission that was the final Hemi Cuda built had a bid of $4.1 million in 2005 without a sale.

This car set for Mecum's Seattle auction on June 14 purports to be only one of two Hemi Cuda droptops built with a four-speed transmission, and of that pair the only one with its original engine. Hemi Cuda prices came back to earth following the recession, but have recovered to well beyond $1 million for authentic but less-rare examples in recent auctions. Given the soaring values for authentic American muscle cars — like the $3.85 million paid for a 1967 Chevy Corvette L88 earlier this year — Mecum expects the Hemi Cuda to bring about $4 million upon sale, along with further confirmation of just how far we've come since 1971.