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When searching Mountebank I came across this Italian masterpiece, for sale at Christies. The oil painting's estimated value is £15,000 - £20,000 ($23,000 - $30,000)Size 33¾ x 24½ in. (85.5 x 62 cm.)

A Mountebank Dentist

It has an inscription 'Il mondo è tondo... Chi non fa navigar va al fondo' in the upper left. (I have yet to find translation for it).