Well i just happen to have on my desk a book called "Needlework and Embroidery Tools" by Eleanor Johnson. It says:
Very attractive signed and hand-painted thimbles were made by Roayal Worcester until 1985, and others at the Caverswall Pottery. Numerous other transfer-printed symbols are freely available and appear in some private collections.
Silver thimbles occur in a wide variety of styles and decoration. Some have a semi-precious stone in the top or set in the lower band, or they have designs and messages engraved round the lower edge. They were made as commemorative souvenirs, for example for a jubilee or coronation, and sometimes to advertise a product. Some silver thimbles are enamelled, and these can be very attractive. Gold thimbles are also interesting to the collector and, though not always hallmarked, are desirable, but expensive.
One of the most serivceable thimbles was that which appeared under the trade name of Dorcas. It was made from a layer of steel sandwiched between two layers of silver, this type of construction making it particularly durable. Three other similar types were made, under the names of Doris, Dreema and Dura.
Don't worry, I'm an archaeologist, so I always have all sorts of odd books on my desk!