Hi, Christine!

It would depend on how far back they want you to go.  The abstractors I've talked to in this area (southwestern PA) who do coal searches tell me it's better to charge hourly, rather than a flat fee, because you never know what you're getting into.  You say you've done these before, but I understand they do tend to be quite involved. 

Another caveat is that in some PA counties, coal interests are no longer subject to assessment as surface interests are.

Where in PA are you located?  Just curious.

Regards,
Scott Perry