Thank you for the good insight, and I apologize for the late reply! I do not know the age of the Santa Fe diesel, as my (deceased) brother was an avid train collector, and had been acquiring Lionel trains for a long time. The locomotive number is "2343". The side ladder to the cab has 2 rungs. There is a "GM" logo on the side near the aft end of the engine. When I slide over the battery holding plate, there is an imprinted number  "2333-20".

It is good to know that 9V may be too much for the horn actuation! I will have to disassemble the engine from the housing and check this out more. I hope to get to this in the next few weeks, after we did out from all the recent snow and ice in Connecticut!!

aaganz