“WD7S� is another series name that occupies the first four digits of the model number of its guitars. I suggest you contact the manufacturer and ask if there are records in the company archives which can give you and idea of the age of the instrument: There is also a discussion forum for those who are interested in auto harps: Autoharp Talk: You will need to register (free) to post a question. There is NO additional cost to you at all. Can anyone tell me how to decode the serial number on a Washburn? November 2018 As you have noticed, Oscar Schmidt has been there for about 148 years. Where do i find the serial number Posted by Anonymous on Mar 09, 2014. November 2018 There are no published serial number databases for Oscar Schmidt. Schmidt manufactured ukuleles, banjos, mandolins and other folk instruments alongside guitars. So I suppose if its under that price your getting a deal. These also have rosewood fretboards, but the electro-acoustic models have MET-A07 preamps.