Sure is purty..
You can clean the rust off that marble using a Brillo pad under running water. Some marbles I can only guess at the manufacturer so get classed as a 'West Virginia swirl'. Age dating is a lot easier. The dump I'm presently working outside Trona,Ca is a large canyon where garbage was dumped from the 1800s to 1954. Thousands of small,seperated,individual dumpsites. First thing I do is determine if a particular dumpsite is commercial or residential. Residential sites mean you'll find lots of personal items,such as marbles,tokens,etc. I'll look for what I call 'marks' such as broken pieces of jade green McKee glassware. Or pieces of Akro Agate childrens' play glassware or pieces of Depression Glass.
Look around for pieces of purple 'desert glass'. All these things give you specific eras. It's a good bet your marble dates to the 1930s/40.