|Manufacturer||Von Duprin Exit Devices|
The Von Duprin 55 Dog Screw-090053 is the newer version, meaning less then 25 years old. It measures 3/8" diameter by 1/2" long with 14 threads per inch. They did have an old style that was available up to a few years ago that had 15 threads per inch. If you have any old style I would recommend the D100 Panic Bar Retainer.
Von Duprin part # 090053