Spark plug collection was on display at the annual Santee car show (which was bigger and better this year)

 Some very cool innovations in spark plugs were tried in the first couple decades of automobiles

 the one on the right is a primer plug.. you'd drip a little fuel into it to help it start... because fule pumps hadn't been invented yet. Fuel tanks were gravity feeding the carbs, which were frequently low on the side on the engines
here is the advertising for the primer plug https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEghf3Oo4ILSyb-GqJm1pG6_QxjChc3MtYEU0w1tmNgqF6Dvjwujj72E5dYRwYARb1xiCc06ciw-LTPsq9LYnsAfoaG2LJLm7qPdiNI3kh_79ymuTJBgu93tk10CZ_-2dHNoUmxT8qDQ6Q/s1600/1918-Champion.jpg

 This mirror is helping to show the fan that the designer thought would help cool the spark plug... but it wasn't very well attached and fell into the cylinder often enought to bankrupt the company in lawsuits.

 here are a variety in electrodes

 the above at left are both mica... because no one had perfected porcelain.. and now the material (according to Wikipedia) in sintered alumina.
The middle has another variety of electrode

 the long electrode was near enough to the piston to get a spark... how I don't know, as the piston to con rod is oil film insulated, and so is the con rod to the crank, and also the crank to the block. So how the electricity in the ignition was working is a mystery to me

 terrific variety

For other spark plug collections: look in the first dozen photos in Jim's post http://justacarguy.blogspot.com/2008/06/tour-with-jim-86-yrs-old-who-still-has.html

and a smaller collection display at the Antique Gas and Steam Engine Museum in Vista https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjgU-XCS9cZTRpvsLuQKxj2PAT6hOwCjOLlohxoL-JnIF3SagUoEPyxkD8JWFd9SnIFWz84v9uKtxCyIKz9VZ2IRgUq2qaVph8uWWRB02DICgcnb5howQgEXCE3mcWJx3yJZjPrXPJyLW8/s1600-h/DSCN3648.jpg