A commemorative coin for the 300th anniversary of the founding of the Province of Maryland was first proposed in the US Congress via a bill intorduced in the Senate on March 6, 1934. In a show of bipartisan collaboration, the bill was introduced by Senators Phillips Lee Goldsborough (R-MD) and Millard Evelyn Tydings (D-MD).
The bill called for 10,000 50-cent pieces of standard size, weight and composition to benefit the Maryland Tercentenary Commission. Upon its introduction, the bill was immediately referred to the Senate Committee on Banking and Currency. No Hearing on the coin proposal was held, but the Committee did quickly take action on the bill and issued a favorable report, without amendment, on March 13, 1934. The bill was considered and passed by the full Senate one week later.
The bill was then sent to the House where it was referred to the House Committee on Coinage, Weights, and Meaures. The House Committee also reported the bill out favorably, but only in conjunction with several recommendations for amendments. The most significant - and the one that impacts collectors the most - was the amendment that changed the coin's proposed mintage from 10,000 to 25,000. This change moved the coin from being a potentially sought-after key type within the series, to just "one in the crowd."
The House agreed with the Committee's recommendations, passing the amended bill on May 2, 1934. The updated bill was then sent to the Senate for its reconsideration. Just a day later, the Senate took up consideration of the amended bill and concurred in the changes made by the House. After that, the only remaining hurdle was approval by the president. On May 11, 1934, President Franklin Delano Roosevelt signed the bill into law and Maryland got its commemorative coin!
Side Note: The Maryland Tercentenary was the second commemorative coin bill to be signed by FDR; the Texas Independence Centennial half dollar bill was the first (Jun 15, 1933). The Arkansas Statehood Centennial (May 14, 1934) and the Boone Birth Bicentennial (May 26, 1934) coin bills were close behind the Maryland. Though approved second, the Maryland coins were struck before the Texas coins due to the Maryland coin's approval coming nearly half way through the anniversary year it was meant to celebrate - it was a more pressing matter (no pun intended).After strong early sales amounting to approximately 15,000 coins at $1.00 each. Sales slowed dramatically in 1935, but the Commission was able to sell about 5,000 additional coins early in the year. Eventually, however, the Tercentenary Commission began to offer discounted pricing for its remaining coins, especially if purchased in bulk, in order to dispose of its inventory. Commission sales appear to have closed in April/May 1935.
In the end, all 25,000 coins struck were distributed into the marketplace; none were returned to the Mint to be melted. It seems clear that had the language in the original coinage bill been authorized, the Maryland half dollar would have been a quick sell out and a marketplace frenzy would have ensued with significant price escalation witnessed. The revised number, however, appears to have been just about ideal in terms of supply and demand, and a good model for future coin proposals.
1934 Tercentenary of Founding of the Province of Maryland Half Dollar

To learn more about the Maryland half dollar, check out:
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1934 Maryland Tercentenary-
1934 Maryland Tercentenary - Revisited-
1934 Maryland Tercentenary - Hans Schuler-
Official Seals on US Commemorative Coins - Maryland-
Coins With Hats Thread - Maryland TercentenaryFor other of my posts about commemorative coins and medals (plus failed proposals!), see:
Read More: Commems Collection.