Intel ME firmware binary, version 9.5.3.1526, with SLM in the name, most likely the slim SKU, and PRD EXTR, likely a production image extracted from a dump.

BIOS package for the Dell Inspiron 1525 and 1526, model code PP29L, on the Wistron DS2 Intel Spears platform with board 07211, the trailing 91 not explained.