Mystery Omni-Directional Siren my Uncle collected

[KaizoMach3]

I'm pretty sure it's a Mach 5, knowing the dual headed Fedelcodes only came in 3 hp, 5 and 10. Also, I think there's a 50% chance there's enough space for two shrouds, since the siren has a similar build to Glandorf's Fedelcode. I ain't no expert, but it doesn't sound too far fetched. Someone said in this post it was in storage for a while before being taken out and sold on ebay.
One thing to point out is if this is a later dual headed model? Given rotor pictures were posted a while back, showing straight vanes in the design.

It is not a 5. The owners themselves said they found a 7 on the tag.