The HAGI classic car index advanced 11.7 points to 254.8 in July, up 4.8% on last month's total and a new all time high.
Sales in 2014 had been in a slump, but a string of major sales throughout the month galvanised the market.
More sales throughout August and September (including Pebble Beach, Goodwood and RM Auctions' London auction) are likely to continue the trend.
Ferrari stormed up 7.4% to 274.2, demonstrating an impressive rise of 20.2 points, while Porsche made up 12.1 points to 244 - equating to growth of 5.2%.
While these figures represent a significant improvement in the value of the market, they fail to match up to last year's unprecedented growth.
This is not necessarily a bad thing, however, as HAGI warned that prices then mirrored those seen in the 1980s just before the Ferrari bubble burst.
To date only Ferrari and Porsche have managed to break into double percentage increases.
Growth for Mercedes and BMW stands at 1.6% for the year, a figure that just raises them out of last month's negative growth.
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