(from Clash of Arms website:)
The Command at Sea Player's Handbook is a 32 page compilation of all the charts and tables contained in the 128 page Standard Rulebook. It also includes errata from the first edition, and it is also compatible with the second edition rule set. Use of this playing aid greatly assists the flow of play in multiple player games, as all of the data is right at hand, along with references to the appropriate section of the rulebook.
(from Clash of Arms website on 4th editon:)
Updated and for use with the 4th Edition Rules as released in "Atlantic Navies" and all upcoming Admiralty Trilogy products