[CR]Campagnolo pista hubs lock rings: different sizes?

(Example: Framebuilders:Pino Morroni)

From: "Anderson, Robert" <randerson2@grey.com>
To: "'classicrendezvous@bikelist.org'" <classicrendezvous@bikelist.org>
Date: Mon, 20 Sep 2004 11:31:05 -0400
Subject: [CR]Campagnolo pista hubs lock rings: different sizes?

I just noticed that Campagnolo track hubs from 1973 (no oil ports) have a different sized lockring from later Campagnolo track hubs (probably early 80's, with oil ports/clips). The older hubs have a slightly larger thread diameter. I'm curious as to when this happened, and also why? Just seems like a strange thing to change.
Rob Anderson
Brooklyn, NY