The Michigan State Police used some of these in 60's and 70's with a red lense. Living in Mi. you would think there would be some around. Nope. Glad you found one.Same type of light made famous in the original Hawaii Five-O! Had to replace pilot light post and bulb. But otherwise works well!
Do you have the thread on that? Just searched for 30 minutes and could not find anything.The benefits of the oscillation of the model 174 have been discussed here before. To put it in a somewhat more modern context, consider the effectiveness of the Magnabeam versus the Firebeam.
If I recall correctly, the 176 came out some years after the 174 for applications where the an oscillating beacon would not necessarily be desired.