$700 is lower end price of a collector 98% DS. For that money it should come with an appropriate box in good cond. Since it's a shrouded barrel they're "supposed to be" O.K. with +P if you're fond of that load and intend to carry the gun. Even then a steady diet of +P is not recommended. The DS/Cobra/Agent has had the "short butt" since '66. Those type grips are much easier to find than the "long butt" grips should you want replacements. Timing is all important on these guns and the tests for timing on a Colt are different than S&W tests. If you're unfamiliar with Colt test go the Colt Forum and check out their sticky on the subject.
Parts for these guns are hard to come by. It's to the point some parts are being rough manufactured by skilled hobbiest machinists and once you buy the part you need to find a gunsmith very familiar with Colts to install it.
I realty like the DS format and carry an agent or Cobra regularly.
The only DS I have now is on the lower right of pic. The others are 2 Cobras and 1 Agents. The gun on the upper right is a well finish challenged Cobra I got 2 weeks ago for $155. Lockup on all these guns is perfect, though they range in finish quality the DS being about 96.6786%.