[Perpetual calendar] [object]

Title supplied by cataloger.
Date from dealer's description.
The circular ivory object comprises a center component with two lids, one on each side. One lid unscrews to reveal a dial with two concentric charts under glass (broken) and on verso an ivory knob permitting the calendar to turn. The outer chart lists the Dominican letters A-G and the corresponding dates and months of the year. The inner chart lists the days of the week. Attached inside one lid an engraved table of Dominical letters, Old Style, covering the years 1700-1752, and New Style covering 1700-1799. The other lid has an engraved table of Dominical letters, New Style, covering 1800-1900.
Only in 1752, did the Gregorian Calendar replace the Julian calendar in England. This calendar was used to determine the day of the week of any date during the 18th and 19th centuries in England.
"5162 TRNX"--inscription in pencil on label attached to lower lid.