He's right. It is a C series, and judging by the open motor, it originally had a chrome rear housing. The underhood C4 siren had a brush cover over the rear of the motor. Now what would be fun would be in guessing which model it had been. You've got three choices for outside mount: C5G, C5L, C6. The C5G, which had the grille front, was an extremely popular model. For that matter, so were all of the C sirens with their extremely long roll and deep, mellow sound. Now that I've done this much, I'll let someone see if they can identify the other two models: C5L and C6. Federal also offered some other options. Can you name them? Shouldn't be too hard!