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Hi Sean,

I have purchased from Concise directly. They are very easy to work with and you'll get a nice new slide rule for far less than used on Ebay auctions. If I recall correctly just fill in the order online and submit, they will then email you with final charges(mailing) and request a credit card # for payment. I have a No.300 and a Stadia. Two things I really like compared to Pickett/SIC circulars:  1. the trig scales are divided in degree/minutes (vs degree/decimal degrees). 2. the scales are printed to read up from the center so that you can hold the bottom of the rule and read on the top (opposite of the Pickett/SIC).