Actually, I have put in a formal request for interpretation on this matter last year but, I'm still waiting for a response.
The way the book is written if you qualified 514 Gr. B to 514 Gr. B then you are ONLY allowed to weld 514 Gr. B to 514 Gr. B because it has to be the same "grade/type" or specific Table 4.9 steel per Table 4.8. However, I think the intent as demonstrated by Note 2 on Table 4.8, Table 4.9, Table C-2.4, previous editions of the code, the ASTM standard for the material and simple logic is that you'd be allowed to weld and 514 2-1/2" and under to any other 514 2-1/2" and under (i.e. grades A, B, F, H and S). And, possibly thicker grades of 514 (i.e. grades E, P & Q) as well based on Note 2 in Table 4.8. However, until they respond to the request for interpretation we'll never know.
However, I've got a potential short cut for you: What year or to what edition of D1.1 was that coupon run too? Section 4.2.1 of AWS D1.1-2006 accepts qualifications to older editions of the code if they were the governing standard at the time. Many of the older editions were alot more lenient with what you'd be allowed to do with your 514 coupon.