At least four companies used the shield shaped indicators; American, Boyle-Dayton, Doty and Milwaukee. American, Doty and Milwaukee all used the same style with two rivets through the face holding on the tension clamp and meniscus line which were all one piece. American used it on several of it's models.
Doty sales literature only showed etched cylinders but almost all photos I've seen of Doty's have the shield. This doesn't mean they were original to the pump.
Milwaukee had it's own unique shaped indicator but for some reason used the shield on it's 297 & 299 model.
Boyle Dayton used the shield but did not use the spring tension to hold the indicator to the rod. It had its own style of clamp, tightened by a screw to the rod. It's design eliminated the need for rivets through the face.