Yup. I'm sure. I'm kind of an authority on cartridge development from the Civil War until the advent of smokeless powders in the 1890s.
That you may very well be.
And while you are semi-correct regarding it's original name. It was originally called the Winchester .38 Central Fire and later referred to simply as the .38 WCF or .38-40. It was originally available, depending on manufacturer in loadings of either 38 grains or 40 grains of black powder, it should have been called either the .40-38 or the .40-40.
So what we commonly know today as the .38-40 Winchester has been most commonly called the .38 WCF or .38-40. However it has also been known as the .38 Marlin, the .38 Remington and the .38-40 Colt. This is because there were already the smaller, straight walled .38 Colt and .44 Colt cartridges.
If you search you can find referrences to .38-40 Colt ammunition and even chamberings. Especially in regard to the Lightning Rifles and Carbines.
I have seen .38-40 Colt (as well as .44-40 Colt) used both on ammunition box labels and in catalogues. You can also find .38-40 Colt & .44-40 Colt headstamps as well as .38 Marlin and .44 Marlin. I know because I used to have one each of all four in my collection.
Regarding firearms, just this past Saturday, I was fondling a immaculate, Colt Baby Lightning rifle chambered in (according to the barrel markings) .44-40 Colt.
It was only $5,000. I didn't buy it since it didn't have a picatenny rail or a bayonet lug.
When I was young, I knew a small town police officer who actually carried a Colt New Service revolver chambered in .38-40 Colt. I remember it so well because it was the first one I ever saw. At that time I had heard of the .38-44 but not the .38-40.
I don't know how old it was but there wasn't a spec of rust nor of the original blue to be found on it. I know it sure was a lot smoother to shoot than my Grandfathers 1892 Navy and it kicked a heck of a lot more.
He told me his Chief told him he could carry any .38 caliber revolver he wanted to. He said it was the biggest 38. He also said that .38-40 Colt ammo was for revolvers and .38-40 Winchester was higher velocity meant only for rifles.
Now I personally don't consider myself to be an authority on anything but I do know I have seen a gun (and ammunition) marked .38-40 Colt.