The “Banana” whistle, referred to above, was a WS-36/37 designation. There is a good source of information located on Olsen’s Library. The website is presently working, so I suggest taking a look. Just search in the Prewar section, & likewise, under the Whistle section. It has a wealth of info, with diagrams of all the whistles produced by Lionel. It will take some digging, to get to the section you need, but is well worth the research. I’m on an iPad, right now, so I can’t give the steps to get to the requested info. Good luck.
The Olsen Library has Postwar & Prewar sections, and an alternative is to purchase their CD’s, depending on the era of Post/Pre war.
