Hmmm, I am 99.9% sure it's one of the B-29-35-MO range built by Martin in Omaha. The numbers I can see when enlarged are 4272x4. The x is the part that is unreadable. Looking at serial listings for the B-29, it would be one of 4 from the same lot (B-29-35-MO);
44-27264
44-27274
44-27284
44-27294
Looking at the Robert Mann book on the B-29,
44-27264 was listed as "Wild Goose" with the 301st BG, written off 11/21/1952 (damaged in landing accident at Barksdale)
44-27274 was listed with no name also with the 301st BG Written off and reclaimed at Mountain Home 7/18/1954
44-27284 was listed with no name with the 4141BU written off and reclaimed at Pyote 9/15/1953
44-27294 was listed with no name with the 9th BG, written off and reclaimed at Hill 8/19/1954
Interestingly, the name "Precious Cargo" is not listed in any of the B-29 listings that I have seen, so it is a bit of a mystery.