Jon Gruden's playbook was the one that Callahan used in his time with the Raiders. There is no "Bill Callahan" offense per se but it was all Gruden's WCO. I browsed through a minicamp playbook from the 1998 Oakland Raiders and the terminology is completely different from the Coryell offense. There is no practical way to implement that offense without having the players learn the terminology. While it may be easy for the wide receivers, the OL will have to learn two new sets of protection calls which again is pretty impractical. The only way I can see it work is if Callahan actually translates one play at a time and converts into Coryell terminology. That is entirely way too much work on one person to do by themselves and if the protection schemes are different in any way, well now Callahan is "making up" new terminology. WCO's do not use a numbering system to designate routes but instead use the actual word like "dig, corner, go...etc" so it would be pretty easy for the WRs to pick it up, however, some of the playcalls are incredibly lengthy. This presents a problem for Romo having to digest this and the Coryell while relaying the plays on the field. For example: HARVEY FAR WEST RIGHT ZOOM 200 JET HAMMER is play from a 3WR set that attacks the seams with TE and slot WR while the outside corners running stop routes or fade routes on cloud coverage (cover 3). Callahan should be able to use the most basic plays in Gruden's scheme and find something in the Coryell book that has the same attacking concept. All playbooks have the same principles when attacking the defense (man or zone) The differences are how they do it in the formations. Something else to consider is that with Callahan calling plays it gives a new "set of eyes" to look at the Coryell scheme and figure out the strong suits of it with our current personnel/future personnel. Sometimes when you do something a certain way for a long time you can get complacent with it. I've had that happen to me a few times in my job and I'm always open to learning a new method of doing things. Hope this clears up some confusion.