All of the early blue receiver Red Labels had fixed chokes. The blue receiver 20 gauge went to at least 400-41000 and the 12 gauge went to only about 400-03144, of which only about 419 blued chrome moly steel 12's were made in addition to 1,000 chrome moly steel Ducks Unlimited 50th anniversary guns which had an electroless nickle finish.
There were however at most a few hundred each of a model ordered by the outfitter ORVIS which had blue receivers (20 and 12 gauge) which were also the first of the multi-choke shotguns.
For the 20 gauge they appear in the 400-56xxx/400-57xxx range and on the 12 gauge in the 410-56xxx/410-57xxx range.
Chet15