This is according to webtender.
http://www.webtender.com/handbook/measurements.html
1 pony = 1 ounce
1 jigger/bar glass = 1 1/2 ounces
1 shot = 1 1/2 ounces
A "shotglass" is usually 1.5 ounces, but sometimes 2 ounces with a measuring
line at 1.5 ounces. You can also buy (in US) "short shot" glasses or "pony
shots" which are 1 ounce. Pony shots are usually used with martinis,
manhattans, and rob roys.
I wish they would come up with a concrete standadization for measurements.
Until there is, we will keep discussing the same thing over and over again.