The initial policy of selling patterns and proof coins was intended to suppress speculation. The same applied to small circulation mintages in the 1880s. That never worked. Changes to Mint Regulations dated October 10, 1887 were generally effective at suppressing pattern piece sales. (1896 and 1907 being the primary exceptions.) Here's the most active section of revised regulations:
4. Experimental pieces of proposed designs or of new coins for the official use of the
Director of the Mint under Section 3510 R.S., and on his written requisition, shall be
struck in such metal or alloy only, and of such weight and fineness, as prescribed by
law for coins of the same denomination. Such experimental pieces will be receipted
for by the Director, and if not adopted for regular coinage during the same year, shall
be defaced by him as soon as the use is subserved for which they were struck, and
forthwith returned to the superintendent, who shall cause them to be melted in his
presence, and that of the melter and refiner, when both of these officers shall join in a
written statement to that effect, which statement, to be sent to the Director of the
Mint, shall be a voucher to the Director of the Mint, and so put upon record in the
regular archives of the Bureau of the Mint. Such pieces, if adopted for coinage, will
be returned by the Director, and receipted for by the superintendent.