Just to clarify the match between face plates and models:
Interceptor sirens (blue face and plexiglass panel):
The PA20 has wail, yelp, and alert tones.
The PA20A has wail, yelp, and hi-lo tones.
Director sirens (brown metal face plate):
The PA15 has wail, yelp, and alert tones.
The PA15A has wail and yelp tones only.
As I said to Ryan before, the repro labels and face plates look great.