2017-S Effigy Mounds, Silver Proof

San Francisco opened the 2017 silver-proof slate with Richard Masters's Effigy Mounds design at 522,526 pieces, the figure matching the U.S. Mint's reported Silver Proof Set sales for 2017 and a modest uptick of roughly 41,000 pieces against the 2016 silver figure. The increase reflects the 225th anniversary of the U.S. Mint (founded April 2, 1792) and the elevated collector interest that year's commemorative product lineup generated. The reverse renders three of the Marching Bear group at the Heritage Addition in northeastern Iowa, the bear-shape effigy mounds raised by the Late Woodland period builders between roughly 750 and 1400 CE along the bluffs above the upper Mississippi River. The composition is the 90% silver, 10% copper alloy at 6.25 grams with .1808 troy ounces of pure silver, the standard silver-proof quarter alloy from 1992 through 2018. The issue is the first of five 2017 silver releases and the 36th of the 56-design ATB program.

Authentication on the issue starts with weight. The 6.25-gram silver planchet against the 5.67-gram clad sister gives a calibrated jeweler's scale a half-gram spread to resolve, the cleanest non-destructive separation. The reeded edge reads silver around the perimeter without the reddish copper-core line a clad piece shows at an angle. PCGS, the Professional Coin Grading Service, and NGC, the Numismatic Guaranty Company, attach a Silver or S/Ag attribution to the slab insert alongside the proof grade and a Cameo (CAM) or Deep Cameo (DCAM) contrast designation, where DCAM is the standard outcome rather than a premium upgrade because the working dies receive chemical etching before each press run. Strike diagnostics on the issue sit at the low-relief mound contours and the surrounding bluff-edge texture, both of which require careful die polish to keep the boundary between mound silhouette and grass-covered ground readable. Population counts at PR70-DCAM run into the thousands.

The collector market positions the issue as a 2017 Silver Proof Set component priced against the silver-spot floor plus a slab fee. PR69-DCAM examples in PCGS or NGC holders move at a modest premium over the bullion value carried by the 0.1808 ounce content, and PR70-DCAM examples sit a tier higher with registry-set buyers driving the spread. The mound-builder cultural subject draws cross-disciplinary appeal from archaeology and Iowa state-coinage collectors that the year's other designs do not generate. The 522,526 silver print run sits at roughly 48 percent of the 1.08-million 2017 clad-proof figure. For the broader story of the ATB Silver Proof program and the series' production arc, see the Washington ATB series history.