Help identifying Sylvania tube.

Highvswr

A friend tossed me a couple old tubes; one being a JAN 5Y3WGTA in the box (very tattered). The other I have not had any luck identifying on the internet. The tube is the size of a 12AX7, horizontally marked ( in green)
ACL
SYLVANIA
Made In USA
And marked vertically.
552
These are the only markings on the tube I can find. I have a pic but appears to large to upload.
Any ideas and why so hard to find?
Thanks

Full Name
Robert Trombley
Music Man Equipment
212 HD-130 (2475-130 Tube PI)

Member for

5 years 9 months

Highvswr Sat, 04/20/2019 - 17:30

Sylvania tube pic.

Images