The FWB models have undergone changes over the years as they introduced new improved models. There's a page with schematics and manuals for the rapid fire models in their order of introduction C5, C55, C55 (after serial #5000), C55P, and the latest C58.
http://www.feinwerkbau.de/ceasy/modu...p5?cPageId=231
P58:
http://www.feinwerkbau.de/ceasy/modu....php5?id=565-0
C55P:
http://www.feinwerkbau.de/ceasy/modu....php5?id=578-0
C55 Post #5000:
http://www.feinwerkbau.de/ceasy/modu....php5?id=576-0
C55:
http://www.feinwerkbau.de/ceasy/modu....php5?id=577-0
C5:
http://www.feinwerkbau.de/ceasy/modu....php5?id=577-0
Other companies that make very similar models include Walther and Styer.