A rose engine lathe (Wikipedia) is a type of geometric lathe used to produce complex radial engravings called Guilloché, which are used both for decorative and security (i.e. anticounterfeiting) purposes.
Those of you with more than $238,000 of disposable cash lying around may be irked to discover that the auction for this stunningly beautiful antique specimen is long closed. At least we can all still enjoy the gorgeous photographs, courtesy Massachusetts-based Skinner Auctioneers, who sealed the deal back in December. Their site is actually chock-a-block with beautiful old tools, instruments, and apparatus, and has proven to be a major click trap for me this morning.