You were very close to being correct. Actually, now that we are so far in the 2000's, an antique is anything from 1917, and they had electricity then! Before then, there were quite a few lights that ran on gas, and these would have had hollow arms too.

If a light has those solid arms you are talking of, you know they are SUPER old, and definitely date back to before 1820.

history lesson concluded 😎 😎 😎