I went directly to Mr Coffin and asked. I will try to find more information if I can. Anyway, here is his reply:
Good to hear from you. Here is the list. Sorry I have not included more details, and drawings, but at least this is better than nothing. I am spending most of my time now writing and lecturing, mostly about things unrelated to puzzles..
List of Recent Puzzle Designs by Stewart Coffin, October 2007
This list begins where John Rausch?s AP-ART Compendium leaves off, from #191 in 2003 up to the present #223.
#191, Chicago . An improved version of #119 with right-angle cuts rather than diagonal on the end blocks (but see #206), so named because first sold at IPP23 in Chicago .
#192, Prism Cell. My design notes for this one are lost, and I have no model, but see #200. I probably made and sold about half a dozen.
#193, Computer Killer. Five polycube pieces, one with hidden swivel joint, fit into a 3x3x3 cubic box. Was exchange puzzle at IPP26.
#194, Triple Play. Four L triominoes fit into a 2x2x3 box with sliding cover three ways. Improved version #194-A uses checkered pieces.
#195, Box Rebellion. Might be considered a variation of #194. Used by John Rausch for IPP24 exchange.
#196, Tray Bien. An improved version of #87-A. Seven pieces and a set of four two-sided trays. Simplified version have been used as an exchange puzzle at IPP24.
#197, Under Cover. A four-piece variation of #19. A few were made and sold in 2004, but I did not save any and my design notes are lost.
#198, Involution. An improved version of #30 (but later superceded by a further improved version #214).
#199, Blocked Box. Henry Strout exchange puzzle for IPP25.
#200, no name. Same external shape as #115, but simplified. Or, to put it another way, a truncated version of #200-A. I probably made and sold two or three. Similar to #192.
#200-A, no name. Resurrection of an experimental 1980 design. A few made and sold. I still have the original rough model. Third stellation of the R-D.
#201, Victor. Resembles #128 but more difficult coordinate motion. Made and sold a few.
#201-A, Elongated Victor. Even more difficult than #201. Made and sold a few in 2004 in canarywood.
#202, Drop Out. This sliding block puzzle is Henry Strout?s exchange for IPP27.
#203, Square Route. A 4x4 sliding block puzzle with 82 steps. About six made and sold in 2004.
#203-A, Multiple Choice. Variation of above with rectangular grid. A few made and sold.
#203-B, Sunrise . Another boring variation of the above. A few made and sold.
#203-C, The Fox. Boring variation of above with picture of fox. May have made a few.
#203-D, The Flag. Used by Tom Rodgers for IPP25 exchange.
#203-F, Butterfly. Colorful improved version of the above. My entry in IPP26 design competition.
#204, no name. Fancy version made by Tom Lensch.
#205, no name. Five-piece interlocking version of #82, Patio Block.
#206, Polly-Hedron. Improved version of #191. Jerry Slocum?s exchange at IPP26.
#207, The Park. Six-piece serially interlocking polyhedron.
#208, Tripp?s Puzzle. Six polycube pieces fit into a 2x3x4 box eight ways. Very simple. Three made in Jan. 2006 in fancy woods for the grandchildren.
#208-A. Four-color version of above with only one perfect solution.
#208-B. Checkered version of above with only one checkered solution.
#209. Five polycube pieces fit one way and one order only into a 2x3x4 box with L opening on one end.
#209-A. Variation of above, two easy solutions, not very good.
#210. Two kinds of pieces, 5 + 1, fit one way only into a 2x3x4 box with L opening on top. Henry Strout?s exchange puzzle at IPP27.
#211-x-1, 211-x-2, 211-x-3, 211-x-5. All experimental interlocking 3x3x3 cubes of four or five pieces. #211-4 was Bob Finn?s exchange puzzle at IPP26, ?It?s a Knockout!?
#212-x-1. Experimental 3x3x4 six-piece interlocking rectangular solid.
#213-x-1 through 213-x-7. All experimental 4x4x3 interlocking rectangular solids.
#214, Involute. This is an improved version of Convolution #30 and Involution #198. Eight-piece 4x4x4, serially interlocking.
#214-x-2, Experimental variations of above.
#215, Square Dance. Six polycube piece fit into 3x3x3 box with 2x2 opening one way and one order only.
#216. Four polyomino pieces fit into rectangular tray.
#217. Improved version of #216. Jerry Slocum exchange puzzle at IPP27 and my entry in Design Competition. My best flat puzzle design.
#218. Another variation of #216.
#219. Five polyomino pieces fit into rectangular tray.
#220. Variation of #218. Not another!
#221. Six polyomino pieces are arranged symmetrically in square tray with red block in center.
#222, Out-Back. Improved variation of #221. Rearrange four polyomino pieces to accommodate the red rectangular block. Tom Rodgers exchange puzzle at IPP27.
#223. Eight pieces fit into square tray. Pieces are made of isosceles right triangles joined different ways.
Note: I have indicated which ones have been used as exchange puzzle, but there may be others I have forgotten or did not know of. I don?t think many of the others on this supplemental list would make very satisfactory exchange puzzles, but possibly #203-F, #205, or #223. I can send more detailed plans if requested.
I have not been tinkering with puzzle designs lately. Design #223 is dated late 2006. Too many other unrelated projects. (I had three books published within the past year.) Or perhaps just running out of ideas!