The Pennsylvania N5C Porthole Caboose No. 6417 was the first of these porthole cabooses that were produced. First available in 1953, production would continue until 1957. During this period changes occurred to the trucks: 1953-55 bar-end without tabbed couplers, and from 1956-57 with tabbed couplers. But the main variation occurred when Lionel manufactured a version that didn’t have the "NEW YORK ZONE" lettered underneath the number. See the close up above. This version, (B), was only available in set No. 2293W in 1957. Examples of this variation are considerably harder to find.