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R6511 belongs to Rockwell R6500 family of 6502 compatible processors. R6511 is an enhanced version of the MOS 6502 CPU plus on chip peripherals. The enhanced CPU would have been on par with the Intel 8088 or 80286 at that time.
This piece has a very unusual 64 pin package with two rows of pins on each side. The R6502/R6512 are 40 pins each and the 6503.4.5.6.184.108.40.206 are each 28 pins. The R6511 is the only package with 64 terminals and in the alternative arrangement of pins called a GIBE (integrated package of quadruple).
Older wafers like this are great for study under the microscope with large enough feature sizes to recognize circuit components and structures. Modern chips are so dense high power microscope are necessary to view them.