Alan

Yell its a Bill Murray - you have an experienced eye. I wish Bill was still making marbles. He had the gift.

They certainly have a Sparkler-esque thing going on. Nice.

I don't use the term myself because I don't think its helpful. I think you'll find the common usage is a solid core with high transparency, like:

Generally +20% in smaller sizes. As you approach/pass 1" dia. the percentage can increase. This assumes that they are mint.

The seller also says that it is a "Cobra".

Imperials:

To the first pic - its likely dug. The glass was not to temp - resulting in bubbles in the clear.

Its a "plunger". I have a few.

Not Akro - but I understand the comparisons that have been made to large, Akro experimentals.

His hands were shaking so much from emotion when he handed them to me - I told his adult son that I didn't want to take them away from him. He had a lot of memories tied up in the box. They had to have a family discussion and the gentleman smiled and told me that he was ready to pass them on to someone else. His memory of pulling the box out as a boy and looking at it were vivid.

Cool background on that box: I purchased the box from the elderly gentleman who received them for Christmas when he was "7 or 8 years old". He had kept the box all these years.

There are a fair number of modern torch work artists that made Guineas. That particular one is fairly unremarkable in terms of tracing it. It doesn't look like either SP or CR.

Looks very contemporary from those pics.

Its a nice coreless swirl.

I don't know what you mean by "a single pontil solitaire set". You seem to be using that term to imply that the piece in the OP wasn't cane-cut.

Its an End of Cane. From a manufacturing perspective - end of canes should be discarded because it didn't meet the desired design quality standard. That is how we got all of those cane fragments out of Lauscha a decade-plus ago.

I have seen all of those dug. Most were .75" dia. or larger, but usually less than 1". The first pic - that type was in the late digs < a year before digging was halted (not referring to the contracted dig). The yellow is that type is much more often subsurface and twisting through the marble. Same type as this one: The challenge is that most people don't know what they are - and a lot of folks are "book collectors" (they don't buy types not clearly illustrated and described in books - or something with a catchy, stylish Internet nickname). The 2nd one is usually seen dug in smaller sizes. The 3rd one was part of the late digs. I think they are pretty nice looking pieces. A lot of pattern there. The 4th was a standard production type - probably discarded due to the cold rolls.

I like them. All of the above are the >1" dia. patches. (Note the quarter for scale). I bought 90% of them from Roger Hardy back when they were available at New Philly. All of the experimental patches that come up for sale for reasonable amounts - I buy. The big experimental corks rarely come up for sale. A certain seller tried to sell one for $600. for years - with no apparent takers. There are ~24 of the corks known and the quantity of the >1" patches in the quantity noted in my first post. The comparative rarity of both types is very, very, very low compared to everything else that Akro made. There a very few of other large types that Akro made that are also fairly rare.

I'm partial to the Orange and Blue Experimental patches. Roger Hardy told me that there were ~150-160 found.

Get some distance between the lens and the marble. The top of the marble is in focus - but 75% of it isn't quite so. That distance will also allow more light on it without the lens throwing a shadow.