Proof strikings of Capped Bust Dimes, either for collectors or presentation purposes, were first produced by the US Mint in 1820. Production levels were always at minimal levels, relegating this segment of the series to only advanced collectors.
Simply stated, all Proof Capped Bust Dimes are rare, with only a few known for each of the years up to 1827. For some years like 1823 and 1826 no Proofs are known. Within the second part of the series struck from 1828 to 1837 with a modified design, usually around a half dozen pieces exist, at most. The 1832 issue is believed to be represented only by a single Proof example. The 1837 issue is believed to be represented by two Proofs, but they have not appeared on the market since the early 1980’s.
Given the absolute scarcity and the infrequency with which the coins come to market, assembling a complete set of Proof Capped Bust Dimes is virtually impossible. Even the the acquisition of a single example would be a true highlight for the advanced collector.
taken from: http://cappedbustdime.com/