L-1-a Class #3223 (with #3332 helper out of sight later in the train) passing The Stanley Works in August 1946.
Kent Cochrane, Thomas J. McNamara collection.

Although originally purchased as mainline freight power, their inability to operate at speeds fast enough on the Shoreline L-1 class was primarily assigned to the heavy freights from Maybrook. It wasn't until WWII that it was discovered that even the 3-cylinder R-3's or the new DER-1 diesel locomotives could haul as much tonnage over the grades on the Maybrook line.

They continued to haul Maybrook freights until October 1947 when the last of the DER-2a/b/a sets were delivered. By 1949 only 7 (of 50) remained, operating the Maybrook hump. All were gone by the end of 1950.