In what year did ALCO introduce the RSD15 road switchers?

Question

What year did the ATSF (Santa Fe) get thiers?

Answer 1

Acording to the Alco Data Sheet.  They were built 2/1956 to 6/1960

Answer 2

I'm pretty sure it was around 1955. That is when Pennsylvania received their first 6 - the rest of the railroads seemed to have gotten theirs in the 1959-1960 time frame.

Additional Info: The AT&SF got their 50 units between  3/1959 and 3/1960

Answer 3

http://www.urbaneagle.com/atsf/3DSL_1965...