Intel 80487 was introduced in 1991 as a math co-processor for Intel 80486SX family of processors. In fact, the 80487 was more than just a co-processor. It was a full-fledged 80486 processor with integrated Floating Point Unit. When installed into upgrade socket on 486 motherboards, the 80486SX processor was disabled, and the 80487 was used for both integer and floating-point calculations. After upgrade the original 80486SX CPU could be removed from its socket if desired.
Intel 80487 has the same performance as 80486DX CPU. The main difference between them is the pinout.
169-pin ceramic PGA
Intel 80487 co-processor didn't have speed marked on the chip. The co-processor could upgrade 80486SX CPUs running at speeds from 16 MHz to 25 MHz, possibly 33 MHz too.