What significant "improvements" have been made (and by whom) to this Louis Histed classic?

I'm not sure if it would be an improvement but a variation of it, which I also own, is the outer square cabinet was replaced with an open front round tube. Same effect but a different appearance.

As a youngster, I had Abbott's "Round Circle". This was a nice hunk of Magic for $6.50 (now I'm really dating myself!).
You received a heavy copper outer tube with two circular cut-outs, a chrome inner tube, the "feke" and a round brass tray to set everything on. The "new" addition here was the feke being made with a concave section which made the method of concealment much more effective, even at close range. Another advantage to the concave feature is you can insert a wand or even your fingers into the larger outer tube with the cutouts while the feke is in place and it really looks empty!

Later I owned Grant's Daylight Production Tubes which I really think is an innovation. Same basic set-up, but the insides of the tubes and the feke are made of shiny metal. This looks about as "honest" as you can get.

There have been some improvements in the various methods of cutting down the visibility of the black art sections. For example, if you use triple velvet or black triacetate velour for the BA sections and you use expanded aluminum for the grill work, you cannot see the gaff from as close as 18 inches in normal daylight.

Also, Don Redmon had a version that combined the Phantom Tube principle with the BA principle, and even had one that produced a goldfish bowl at the end.

I remember Towne House (or someone like that) having a nice Square Circle with a bird in a cage production for a finale. The cage was as big as the inner tube and stood upright (didn't collapse)!

I don’t know if you call this a significant improvement, but both Don Redmon and Edwin Hooper get my vote as the variety of principles employed.

Horace Marshall made one with a large bush production that was taller than the tube (non botania). Okito (with Redmon) put in the botania load.

Eric Lewis mentioned Yellow Art in his trilogies instead of black art use yellow felt.

I think Fred Hanchen was the one of the first to use the slightly tapered load chamber to ease the loading.

The Haenchen product was known as the Triangle Tube Production. The very clever modification here was the outer "box" was a triangular shape and the three sides were HINGED together. This configuration facilitated a much more convincing showing of the simplicity of the props and absolutly nowhere for the load to be concealed.

I believe George Robinson at Viking owns the rights to all the Haenchen material. This would be a great item to reintroduce to the Magic market.

Right now George has his hands full with all of the other stuff he is trying to manufacture. It is very difficult for him to build the Viking line, the Haenchen line and the Collector's Workshop line and keep the quality up, without introducing new items.

He has just completely re-worked the gumball machine so that it works every time.

But it's not a bad suggestion.

GARY DARWIN in Las Vegas, has created a totally new look to the prop and literally will fool those even that know the principle.

Is his version for sale or is it a personal use item? Where can I get more information on his S.C.
Iven

Although this may better rest in the workshop forum, it seems to fit this thread...

Many years ago, I found two round trash cans that while supposed to be the same size, would actually nest perfectly due to a manufacturing flaw. They immediately became the tube and BA tube for this type of prop.

They were of such a size that they were immediately considered for a head cremation that operated under the same principle. After the bottoms were removed, in the smaller tube, I fixed a partition made from a metal pie pan near, but below the top to become the fire pan (sealed at the seams for obvious safety), and put in separaters to keep the wicking insulated from the metal pan and tube to reduce heat transfer. I then proceeded to construct the prop from that point up.

Being severely budget limited at that time, I opted to make the outer box from dumpster-donated foam core board (department store display signs) attached to a lightweight wooden frame. The neck stock was made from scrap lumber and purchased hardware. The entire outfit was finished, not with paint, but with plain-color fabrics. The decorative fabric was glued on and sealed with a diluted glue mixture (very durable, I found out). The BA areas were treated normally with black felt. The front opening of the box was fitted with cage bars of wood dowel covered with white contact paper.

It worked perfectly for the intended function, but closer to the point of this thread, the prop used in this configuration, would later function to unexpectedly produce a huge rabbit while preparing to do the cremation trick. I also found that by inverting the BA tube, it was basically a square circle with a gigantic load chamber. Thus, I now had a "new" prop that could be used when the cremation trick was inappropriate.

My construction methods have advanced considerably since then, but considering how durable, functional, practical, and cheap this thing was, I sometimes wish I hadn't given it away!

As a point of interest, Mel Babcock made a special run a few years ago of a Square Circle featuring the tappered load chamber. It really wasn't a square CIRCLE, it was a square TRAPAZOID. This was one of a very few of his items that actually looked better in the painted version than in the natural wood.

I also made my own when I was a kid. I decorated a cracker box with yellow construction paper, and blue stars, and moons, along with glitter and other magical symbols. I then used a juice can, which I cut both ends off of to form the tube, and decorated that in blue construction paper, and yellow trim. turned out really well, and I still use it 20 years later! I supported the corners with wooden sticks under the construction paper, and it has held up good.