Was this taken from one of the Solo or Dover books? The monograms which I have seen from these books are all hand-lettered. However, a quick look on MyFonts could probably help you find something similar.

Such as http://www.myfonts.com/fonts/typeart/prints-charming/ or perhaps a little more wildly swashed http://www.myfonts.com/fonts/canadatype/treasury/ or maybe more elegant like http://www.myfonts.com/fonts/fontbureau/sloop/ whatever you use you will probably need to skew it to be upright unless you like the more simple http://www.myfonts.com/fonts/bitstream/typo-upright/