Hartzell 4 blade ID check, Test club or airboat?

[mantiques]

I need help ID'ing this prop.
We recently got in a Hartzell 4 blade propeller and I have called both Hartzell companies (air movement and aircraft division) with no luck to find the ID, can anyone here help narrow it down for me? Thanks!!
design #851
DWG 32834
and another number #21532
84 inches
12 boards laminate
5 1/2 in diameter shaft
8 holes

Is this a test club prop? Navy airboat prop? ventilation prop? Hartzell is stamped on the wood and the scalloped metal. here are some photo's.

[Dbahnson]

It's a test club. Notice how the angle of the blade near the hub is the same as it is at the tip. An propeller used for propulsion will have the angle change along the length of the blade so that the pitch is constant its entire length

See this diagram and note how the angle varies based on the distance from the hub. (In theory, every portion of the blade moves the same distance during each rotation, and since the outer portion moves a much larger distance the angle relative to its direction of movement is less.)

I may have that drawing number referenced somewhere. If I find anything I'll let you know.

[mantiques]

Thanks for the information!! Awesome!
Any information of year? Scallop metal tends me to believe it's early 20's or 30's but what do I know. Would this size of prop be used for testing bigger engines? It would be cool if I could find what factory or state it was used in for the collectors who are interested in buying it from us.
I love digging into historical items or it's personal history so excuse me if I'm asking to much.

Again thanks!!