Summary: Yes, multiple manufactures supplied the horns 1915-1927.
Additional details:
Ref:
http://www.mtfca.com/encyclo/F-H.htm#horn the early bulb horn cars had multiple suppliers and the 1915s are listed as having 3 suppliers. It does NOT address suppliers for 1916-1927. The 1928-1931 Model A Fords had multiple suppliers ref:
https://www.fordbarn.com/forum/showthread.php?t=49464.
The Model T Ford Club International Judging Guidelines 7th edition does not address the horn manufactures for 1917 or similar years. From the photos of the Rip Van Winkle Ford, we know it apparently came with the "cone shaped" rear cover (ref Page 272 of Bruce McCalley's book).
On page 279 Bruce has under the photo of a "cone shaped" rear cover magneto horn: "The magneto horn, typical 1915 to 1922, which mounted on the firewall. Not all such horns were alike, differing between suppliers."
On page 322 he shows a photo of the "top hat" style (rear cover) with the remark: " Magneto-powered horn, typical 1915 to 1927" and across from the photo he stated: "HORNS: The magneto-powered horn was supplied on some production beginning in early 1915, and on all cars from later 1915 until about mid-1922. Beginning in 1922, the electric (battery) horn was installed on those cars with electric equipment, while the magneto horn continued on the non-starter cars. (The date of introduction of the battery horn is not known; 1922 is an educated guess."
And from Bruce's 2 disc CD version of his encyclopedia (available from:
http://www.mtfca.com/discus/messages/822076/844722.html and is highly recommended). John Regan supplied the following information that is included in the CD version that has additional information the printed book does not contain:
"It seems for sure that outside companies were
making the horns. Here is what is posted in the record of
changes for the horn assembly (FN 6432) drawing. The
very first entry in that record of changes is dated
11/29/15 and states: “This drawing was made from a
sample of the horns as they are being furnished by the KW
Ignition Co., and is to be adopted permanently. All
horn companies who are furnishing horns at the present
time are to be allowed to continue with their own design
of horn. Should orders, however, be placed with any new
companies, unless special permission is given by Mr.
Galamb to do otherwise, they shall be required to make
horns as per our K-W blue print.”
Based on the above for sure the cone shaped magneto horn was used in 1917 (ref the Rip Van Winkle Ford). But either style would be acceptable for the MTFCI Stynoski Judging -- unless an update occurs to the MTFCI judging guidelines. (Note they have a page with the updates at:
https://www.modelt.org/judging-guidelines-updates.html (thank you Mark Strange for posting that previously). When I just checked I did not see any updates concerning the magneto horns.
Respectfully submitted,
Hap l9l5 cut off