In all but the very earliest '32 V8s, there is post that is a molded-in part of the outer distributor cap that corresponds to a hole in the inner cap. There was a rubber O ring placed on the end of that post to hold the inner and outer caps together. Remove the O ring and the two caps come apart readily.
(The very earliest '32 V8 outer distributor caps had no molded-in posts and the inner caps had no hole in them to accept the posts of the outer caps.)