|
| US5137452 | 29 Oct 1990 | 11 Aug 1992 | | Base--ten blocks employing single, attachable blocks of one color row of ten blocks of different color |
| US5176577 | 29 Oct 1990 | 5 Jan 1993 | | Rectangular blocks for teaching arithmetic have uniform size joinability and transparency |
| US5238407 | 29 Oct 1990 | 24 Aug 1993 | | Blocks with mating bosses and recesses which bulge for interference fit |
| US5238408 | 9 Jul 1990 | 24 Aug 1993 | | Row of joined arithmetic blocks with common walls which are double end wall thickness |
| US5647185 | 14 May 1996 | 15 Jul 1997 | | Structural blocks and assemblies thereof |
| US6571525 | 1 Aug 2001 | 3 Jun 2003 | | Construction block |
| USD468839 | 26 Dec 2000 | 14 Jan 2003 | Springair 2000 Limited | Set of bricks |
