The Adriatic Type 2-6-4 Locomotive No. 2035 was based on the Pennsylvania Railroad’s Class K-4 Pacific locomotive. The prototype had a 4-6-2 wheel arrangement, however, Lionel’s version of this locomotive was a 2-6-4, which is why their version of this locomotive is classed as an "Adriatic Type." Lionel would not produce a 4-6-2 Pacific locomotive during the post-war years.

This locomotive came with Magnetraction that distinguished it from its predicessor, the No. 2025 and it shares the same die cast boiler casting as this engine along with the No. 675. It has a three position direction unit whose lever is adjustable from the top of the boiler and is located behind the smoke stack. Came with a No. 6466W early tender without the deck rails.

The cab number is heat-stamped on the sides, and the boiler front keystone decal is numbered "5690." Although the four digit number of this engine designates it for use with O27 Gauge track, it will also run on O radius curves. There are two variations:

Variation A: A half-moon-shaped fitting attaches the eccentric crank to the wheel recess. The center rail electrical pick-up rollers are sprung. (1950)

Variation B: Two projecting pins hold the eccentric crank, and the motor armature has cover plates. The center rail electrical pick-up rollers have solid fixed axles. (1951)