Is this the correct button for a 1919. Looking at langs it shows a button for a 1918 to 1925 that looks different. It looks like it has a center post or connection.
That switch was used from 1918-1922.
The long version was eaten by my dog, I mean computer. Summary for USA Fords -- Larry is correct for a non-starter car. Depending on when you believe all cars came from the factory with the combination ignition switch and light switch even non-starter cars used the more simple plain button push horn switch.
For a car that was equipped from the factory with a starter & generator, including the 1919 open cars (ref: http://www.mtfca.com/encyclo/doc19.htm where it clearly states the open 1919 cars were available with a starter:
APR 30, 1919 Acc. 575, Box 11, #732, Ford Archives
T-6604 wood instrument panel for touring and torpedo specified in a letter to the branches.
T-7845, 7846 windshield bracket with integral side lamp bracket used on open cars without starter only. T-7845B and T-7846B bracket used with starter cars (has no oil lamp bracket).
And the open cars with the starters & generators would have had an instrument panel, with amp meter, and a combination ignition switch and light switch. Those cars have would come with the more simpler push only horn button like the closed cars.
Note from memory -- I don't recall if t he combination horn light switch can be used as "only" a horn button. And it is too late for me to look that one up.
Good luck with your T. From the photo you posted showing the switch, it looks like it is in good shape.
Hap l9l5 cut off
The combo horn headlight switch can be used for horn only. I have mi lights connected to a battery, so CANNOT use the combo switch. I have a separate switch for the lights. The original uses a "dimmer" which is the center position. Full twisted forward is bright, full back (clockwise) is off.
Do a search for resistance unit.
This begs a question from me, I plan on using a headlight horn switch for my 1921 TT project, do I need to add a "dimmer" and would the standard wiring diagram be what I follow? In place of a good original "dimmer", what is available?