The value of a 1776-1976 Bicentennial Eisenhower dollar is determined by two primary factors: its metallic composition and its condition. The provided sources allude to the existence of more valuable silver versions, which is the key distinction for valuation.
Most Bicentennial Eisenhower dollars were struck for general circulation and are made of a copper-nickel clad composition. These coins, typically bearing a "D" for the Denver Mint or no mint mark for the Philadelphia Mint, are extremely common. If they have been circulated, their value is generally just their face value of one dollar. In pristine, uncirculated condition, they might command a small premium of a few dollars.
A second, more valuable version was produced for collectors. As indicated by the reference to a "1776-1976-S Silver" coin, these special issues were struck at the San Francisco Mint and bear an "S" mint mark. These collector coins are composed of 40% silver. Their base value is tied directly to the melt value of their silver content, which fluctuates with the market price of the metal. In addition to their intrinsic metallic worth, uncirculated or proof examples in high grades can be worth significantly more to collectors, often fetching prices in the range of $10 to $20, with exceptionally well-preserved and certified specimens commanding higher premiums.
Therefore, to determine the worth of a 1776-1976 Eisenhower dollar, one must first identify its composition by checking for an "S" mint mark, which signifies the 40% silver content and inherently higher value. The common copper-nickel versions are typically only worth face value.
