The sunfish pocket knife pattern is very popular and highly sought after among collectors.  They go by the name sunfish, elephant toenail or just toenail knife.

Case XX Elephant Toenail
1970 Case XX 10 DOT Elephant Toe 6250

These knives are extremely beefy and were meant for rough and tough use.  The master blade is a super thick and wide spear blade and sometimes features two pulls (a nail nick and long pull).  They usually feature a large secondary pen blade as well.  Some of the most collectible sunfish patterns were made by Case, Cattaraugus and Hibbard, Spencer, Bartlett & Co.  If you find an oldie in good shape, you have a great knife!  I appreciate any traffic from these links as I earn a commission at no extra cost to you.