The following 1833 quarter eagles were struck in experimental gold alloys as listed below. None of the 6 pieces is believed to exist today.
The following is from the original 8th edition Judd book draft by Dave Bowers with additions:
"During the years from circa 1820, leading up to 1834, federal gold coins were worth more in bullion or melt-down value than in face value. Accordingly, they did not circulate at par and were available only by paying a premium to bullion dealers, bankers, other holders. Such pieces were coined on demand for depositors who placed gold bullion or foreign coins with the Mint and asked for returns in the largest denomination of the time, the half eagle, plus some smaller requests for quarter eagles. Such coins were largely used in the export trade where they were valued as bullion, not at face value, and were useful in international transactions. In addition, some were coined to the order of the government, who used them to pay certain senators and congressmen who demanded such, and profited from their increased value.
Today, despite generous mintages in many instances, the vast majority of regular gold coins of the 1820s and early 1830s no longer exist, as they were melted down in foreign lands and converted to other coins.
The Act of June 28, 1834, mainly promoted by Missouri Senator Thomas Hart Benton, sought to return gold coins to general circulation by modifying their authorized weight so that they could circulate at par.
In anticipation of the revised coinage standard, Director of the Mint Samuel Moore sent a report to the speaker of the House of Representatives on January 11, 1833, suggesting alloys for the new gold coins. Moore apparently sought to have some silver incorporated, and related:
A gold coin alloyed with about one-twelfth of its weight of silver and copper combined resists the effects of attrition, at least as effectually as any other proportion, the purpose of exhibiting the degree of approximation of the color of fine gold produced by various proportions of silver and copper employed as an alloy of gold coin, a number of specimens of the quarter eagle are forwarded with the report, to which the House is respectfully referred. (The numbers are designated by minute points impressed on the reverse of each coin above the head of the eagle.)
No. 1 consists of 61 7/8 grains of pure gold, being the quantity at present required in the quarter eagle. J49A with one dot above the eagle's head.
No. 2 contains 61 7/8 grains of pure gold and 5 5/8 grains of alloy, making 67 1/2 grains, the weight of a quarter eagle of our present standard. The alloy in this specimen consists of silver alone. J49B with two dots above the eagle's head and simulated above.
No. 3 is of the same weight and fineness as No. 2, but alloyed with silver and copper in equal proportions. J49C with three dots above the eagle's head.
No. 4 is of the same weight and fineness as the preceding, but alloyed wholly with copper. J49D with four dots above the eagle's head.
No. 5 weighs 66 grains, of which 59.4 consist of pure gold and 6.6 grains of alloy, which alloy consists of silver and copper in equal proportions. J49E with five dots above the eagle's head.
No. 6 is of the same weight and fineness as the preceding, but alloyed with silver and copper in the proportion of one part of the former to two parts of the latter. J49F with six dots above the eagle's head.
The first four specimens are of the intrinsic value of our present quarter eagle. The fifth and sixth are conformable to the coinage in which the eagle would contain 264 grains of standard gold, consisting of 237.6 grains of pure gold and 26.4 grains of alloy."
Photo is a doctored scan of the Harry Bass Foundation proof specimen from the Bass Sylloge.