It's beautiful. How on Earth are you finding these? I like this better than the last one.

I can browse sites with this kind of vintage lighting for hours. Really like yours, how wide is it? I would love one for my bedroom but the ceilings are 14' and anything less than a 24" diameter shade doesn't look right.

I would just Google the parts you need including the finial on the bottom. It's amazing what you can find out there. Even try vintage lighting repair sites or collectors' sites. As far as cleaning the rust, I wouldn't try too hard. Vintage is vintage. I wonder what type of metal it is? That would depend upon what cleaner to use.

here is a place to look. you can see what they have without registering, just click on the links to the left hth

Here is a link that might be useful: Chandy Supplier

ooops, I would try Naval Jelly for the rust

eBay and Etsy both have vendors with antique finials, in a range of prices. You could contact the sellers and ask for the interior diameter.

Here is a link that might be useful: One etsy glass finial

I would not bother cleaning up the old steel parts that have rusted beyod passing them over the wire wheel. If they are deeply rusted and fused, replace them. If the chain is solid brass, you can polish it, otherwise replace that too. If the canopy is brass, polish that, otherwise replace it. See the pattern there?
Link is to one vendor of replacement parts for lighting fixtures; there are several others.
Casey

Here is a link that might be useful: Parts for light fixtures

I got this one from ebay last year for $47.

It's 12" diameter.

I searched exhaustively for a crystal fleur-de-lis finial, but came up empty. However lampfinials.com had a section with 3/8" diameter (1/8" IP) openings, and had one with a crystal faceted ball, so I opted to go with that one.

And I bought a set of vintage prisms from ebay to hang around the upper bobeche.

Mr. Weedy's not excited to rewire this one, as the wires are soldered onto the sockets, and I forbade him to use new sockets. :-)

Hopefully we'll have this one hung by the end of the weekend, sans finial and prisms.

Can't help showing these. Old gas lights a friend got a bazillion of out of an old Lake Tahoe Hotel. Re-wired and cleaned up they are really great I worry about the globes as they are unobtaneum French globes. My 3yr old Grandson found a golf ball, stood under the light said "watch this Papa" and the ball did a lazy arc over the globes. My heart was in my throat, but he missed. I have a few more around the house.

The prisms FINALLY arrived today (2 weeks shipping from CA!), so here's the finished product.
{{gwi:2135854}}
{{gwi:2135855}}

Loving the bling. It's totally the centerpiece of the room. I might take a couple chain links out of it...jury's still out on that. It hangs lower than most bedroom lights, but I want the glass column and prisms to be visible.

Beautiful! As long as no one's head is in danger of hitting it I'd leave it so you can enjoy it & the prisms! Very elegant!

Well done!

That turned out great!