in the yale model coding system it goes like this

GLP030UAB085P

GL = Fuel Type LP
P = Tire Type Pneumatic
030 = Rated Capacity 3000lb
The group of letters after the capacity can vary depending on machine Designation, design series, manufacturing source, engine model, transmission and mast type.
U = Special Designation (engine type mazda? probably a UA?)
A = Design Series
B = Transmission Type (automatic 2 speed?)

085 = mast height in inches (collapsed)
P = ? year of mfg?

This was before yale started using thier new serial numbering system which they moved the year of mfg designation into the serial numbering in which the end letter on the serial number would be the year of mfg.

Also from looking at the serial number this lift is definitely old , I'd say built probably back in the late 80's early 90's. Someone else may be able to narrow this down better that has more familiarity with their model nomenclature.

As for this tank on the side.. can you elaborate in more detail what you mean? Is this tank part of the frame?(which in this case would be the fuel tank), or is it a component inside the engine compartment? Need more clarity on this part.