I think a 4'6" is almost certainly UL.
Venerable UL reels compare in size to a 1000/2000 reel made today, while today's 500/800 size XUL reels compare to the venerable Italian Alcedo and Cargem micro reels.
The micro-sized reels are for 4-lb test and lighter, while new 2000/ traditional Mitchell 308/ Penn 716 size has good capacity for up to 10-lb test, especially fishing good fluorcarbon, and you probably wouldn't want to load them with lighter than 6-lb test, mostly because of the amount of line you'd have to spool.



Exceptions are the new larger arbor spools made for braid - many people fish them with XUL mono.
(The 2000 size Shimano I show, I bought for 6-lb braid - only difference from the 1000 size is the spool and gear ratio.)
The bigger diameter new spools are also nicer to your line and lay it flatter for longer casts.
From my experience, there's a notable shock toughness difference between 4-lb and 6-lb, test, (could be a difference in my finesse skills). I personally fish copolymer on the lighter side, and worry less with fluoro (or braid) at 6-lb test.
With light rods and light lines, setting your drag at 1/4 of the line test (with a scale), or if you over-line, at 1/4 of the rod max line rating, is good for both rod and line.
A really good habit, made more important with micro thin lines, is closing your bail manually rather than using the reel-crank auto-bail mechanism. Aside from keeping your hand and mind close to your spool to prevent backlash, it's better on the reel gearing.

I think McFarland would give you a good line and lure rating on any of his blanks.

They often weren't very good about marking recommended line test and lure weight on spinning rods through the 70s. Traditional short UL rods are deep flexing, while the good venerable 6-1/2' L-rated glass spinning rods are fast tapers when compared to familiar fly rods. I've had great examples from Phillipson, still have a great Conolon and my first choice is an H-I Star.
I have a nice Phillipson 7' that's an exception to that fast taper, and it's a brown epoxite registered with spigot ferrule.

Searching this forum, Shane describes a 6' Ameriglass spinning rod as deep flexing, and rated 2-6-lb.
Checking McFarland on Angler's workshop, all Ameriglass UL are rated 2-6 lb., so I would assume all deep-flexing.