The Type I Shield sovereign features the Imperial shield design on the reverse paired with William Wyon's portrait of Queen Victoria on the obverse. It differs from the Type II Shield sovereign by the designer's initials, WW appearing incuse within the truncation beneath the bust.
The design was introduced in 1871 but was changed to the normal WW type before the end of the year and by 1872 all shield sovereigns would have the normal WW on the obverse.
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The absence of a mintmark or the presence of a die number indicate a London mint issue.