The Adriatic Type 2-6-4-Locomotive No. 637 would be available from 1959 until 1963. Lionel designated this locomotive as Super-O, but it shares the same BLACK painted die-cast boiler with the No. 2016, 2018, 2026 (1951), 2029, 2036, 2037, and 2037-500. The WHITE number was rubber-stamped on the cab. It was equipped with drive and connecting rods only, a three position directional unit whose control lever protrudes through the top of the boiler right in front of the cab, magnetraction, sheet-metal trailing truck, smoke unit, headlight with lens and spoked driving wheels. It came with either a No. 2046W or 736W streamlined tender. There are three variations:

Variation A: Has a No. 2046W tender with the number "646" heat-stamped on a raised number board in addition to "LIONEL LINES." (1959-60)

Variation B: Has a No. 736W streamlined tender that is heat-stamped "PENNSYLVANIA," and came with early AAR trucks that has one disc coupler. Occasionally found as part of Set No. 2547WS even though the catalog shows this set with a tender labeled "LIONEL LINES." (1960)

Variation C: Has a No. 736W streamlined tender that is heat-stamped "PENNSYLVANIA" and included with sets No. 2571 (1961), 13008 (1962), and 13098 (1963).

This locomotive was sold in sets that use Super-O track, but it will work equally well on 027 Gauge track as well as the wider radius of O Gauge track.