The #13 Griswold Dutch oven, even without the lid or trivet is worth at least $800, maybe more because it is an early one by the slant logo. The #20 skillet is also worth about $800-900 as is. I'm guessing with the no. 270 it might be an early Erie brand that was bought out by Griswold, but would have to do more research to be sure. A number of possibilities. All in all, you have some great antique Griswolds. No problem in using them, just be careful because replacing them would be very expensive and hard to come by. Like I said, in 30 years of collecting Griswold, I never ran across a #13 with a lid.

Pap