Yep, most clinics send them out because you have to be a government approved lab to run coggins tests and the gov. Has a limit on the number of labs that can be in operation.
Timewise, you figure: the day it was drawn, 1-2 days for shipping to the lab, 1 day at the lab, 1-2 days return mailing to your vet, then 1-2 days for mailing to you. So generally at the quickest it will be about 5 days. Depending on what day of the week it was drawn and whether or not your vet holds the sample for a day or two so that he can ship mulitple samples together (this is more cost effective because of the biohazard requirements for mailing blood samples), whether it was drawn right before a weekend or holiday, etc...it can take up to 2 weeks to get a result back.
Ive never had it take longer then a week to get one back...the clinic that I go to gets a faxed copy from the lab as soon as it is done with testing and I have the yellow copy within the week...i suppose different clinics are different. The lab that they send it to is only like 30 miles away too.