I just purchased an old Shure Green Bullet with a metal handle/ switch and I'm wondering if anyone can tell me how old it is etc.

It's a 520 SLB with what appears to be the original transducer. It's marked Shure Brothers, Made in USA.

Model # 99C86HB

Anyone got any info on what I've got here?...

I'm new to this forum, and have posted this on two threads.