Pennsylvania System" was the service mark or trade name used to designate the combination of Lines East and West.

Adam's and Westlake Adlake Reliable 
Stamped PS in the keystone logo
Correct matching Corning no39 globe also PS embossed.
No.1 bayonet burner.

Condition  - very good,  clean smooth tin , nice chocolate brown patina on the lid and tinned frame .
No heavy rusting or pitting present. 
Fount is clean , burner is free and turning. 
Globe has a yellowish tinge , not a defect , just how the glass was made.
No visible condition issues. 

** has not been oil tested **