Neat-o, I think I just found it described:
Narrative
A handmade marble is a thing of beauty and a technical feat of glasswork and art. While these marbles were made using the "mass production" techniques of the time, in reality each handmade marble is individually crafted by a person. This cannot be said for machine made marbles. Each handmade marble carries with it the individual stamp of the craftsman who created it. This is in the twist of the marble and in the design and the colors. The appeal of handmade marbles lies in their individuality. No two canes were the same, and no two marbles off the same rod are exactly the same. You cannot say that about most machine made marbles.
By definition, a handmade marble is a marble that was individually made by a craftsman. Non-glass handmade marbles have existed for almost as long as there have been children. During primitive and medieval times, these were rounded stone or clay marbles and they are not very collectible today. The handmade marbles sought after by today's collectors are those that were produced in Germany during the second half of the 19th Century and the first two decades of the 20th Century. (Some handmade marbles were produced in England and in the United States during the early 20th Century, but these represented a very tiny segment of the market compared to German marbles). German-made glass marbles represented the bulk of the marble market until the early 1920's. The supremacy of German marbles on the playing field finally ended during the early 1900's due to a combination of several factors. These include the American invention of mechanized marble production, the cut-off of German imports into the U.S. during World War I and the Fordney-McCumber Act tariffs of the early 1920's.
All handmade glass marbles have at least one pontil. This is the rough spot at the bottom pole of the marble where it was sheared off its glass cane or a punty.
Handmade marbles are generally classified as either cane-cut (sometimes called rod-cut) or as single-gather. Almost all handmade glass marbles are cane-cut marbles. This type of marble is sheared off the end of a long cane which contains the design of the marble and then is rounded. Single-gather marbles, on the other hand, are produced one at a time on the end of a punty. Handmade marbles can be further classified by the type and/or coloring of the design.
The production of handmade marbles (whether cane-cut or single-gather) was very labor-intensive. For example, the creation of a handmade swirl required between four and twelve separate manual steps. Single-gather marbles could require less steps, but only one marble was produced at a time, rather than a whole set of marbles off of one cane. In the Society's manual, we will describe in much greater detail the process of making a marble. Suffice to say that the production of handmade marbles was a fairly laborious task. As a result, far less handmade marbles exist than machine made marbles, therefore increasing their value.
The earliest articles discussing marbles as a collectible were published in the mid-1960's. These articles all dealt with handmade marbles. Early marble collectors, and the hobby is really only about 35 years old, were only interested in handmade marbles. The earliest guide to marble collecting was Morrison and Terrison's "Marbles-Identification and Price Guide", published in 1968, followed by Baumann's "Collecting Antique Marbles", published in 1970. Both of these books classified handmade marbles, to almost the complete exclusion of machine made marbles.
The past decade has seen the handmade segment of the marble market mature. This side of the market has not been experiencing the volatility in price that we have seen in the machine made side of the market. This does not mean that handmades do not go through price cycles. Different types of handmade marbles go in and out of favor with collectors, as their tastes change. But, the market has been much less volatile than the machine made market.
I think it is this one:
A caramel swirl is a marble with a dark transparent brown base glass and opaque white bands or swirls in it.
the one we found looks nearly identical, except the swirl is whiter.