Jon
Cross posted. Have you actual copies of the DSGs? I assumed they were exact copies of each other. If you can send me actual copies I can give a better idea as to date. If they are not exact copies then the earlier one could be White and the second copy Saint's reprint. I have some of their work and might be able to compare things like woodcuts and style.
This would also partially explain the estimated dates by the BL. I have a lot of the ECCO material but this has obviously been added since I last got a batch. I don't have access online.