A comparison of three different sizes.
The small one is a Leon Isaacs Lady Falcon (same size as the Esterbrook Lady Falcon)
The medium is a standard 048 Esterbrook Falcon
The "other one" is an Esterbrook 340 Mammoth Falcon. Yeah. It's big.
I actually have a holder that fits it and I tried one that had some rust on unimportant areas. It's quite fine and flexible. But it's not easy to write with. Your hand is so far away from the page that unless you're Andre the Giant you will have some challenges getting a clear, steady hand out of it.
But it's also really fun.