Depends how many cuts you are making, of course. For a hobbiest, it’s a luxury. For somebody trying to feed his kids, some sort of miter box multiplies labor tremendously.
If it is is decent usable shape, go for it. If its a rusty clunker with missing parts, let it go. Hand boxes last more than a couple lifetimes.
If you don’t use it, part it out on Craig’s List or eBay. Just the saw, even a warranted superior saw, ( almost always made by Disston or Atkins) is worth that. If you are doing repetitive work and don’t want the noise of a chop saw, they aren’t much slower. It takes more time to measure than to saw.
I used a Miller Falls box for 25 years and only went electric in the 1990’s because the company I worked for paid half, and the fellows I had to share my box with weren’t very careful. A circular saw blade is disposable and the boss paid for them.
My box could go a couple more lifetimes, but I take care of it ( it has its own box). When I retired it was the electric tool I let go. A hand box will often cut larger trim. And at the end of my career people wanted lots of the big stuff. Most of the abuse the boxes took was on the ride home in the back of the pickup surrounded by shovels.
I have a very nice 28”x 5” saw (tooth line) made for a Stanley box that I could be persuaded to part with if you are looking for a saw. It still has 4 3/4” left on the plate. It turns out Stanley saws use a thicker plate than Miller Falls provided, and changing over every time I want a sharp saw is not a simple task. It’s quicker to just sharpen the saw.
And when you get it you can haul the saw out when people start bragging about their big dovetail or tenon saw.
( Stanley #4 for scale )