I found the 1980 version of the AMI MOS Products catalog: http://electronicsandbooks.com/eab1/manual/Electronic%20Component%20Databook%20Datasheet/Brand/AMI/Databook/1980%20AMI%20MOS%20Producs%20Catalog%20c20120824%20%5B512%5D.pdf

Sure enough, it lists the S2152, and the pinout matches the Wildfire PCB. "The S2152 is an extension of the S2000/S2150 and is software compatible with them. It has the following enhanced features:
Digital-to-Frequency Converter (4-bit)
Programmable Divide-by-N Counter/Timer
15 Outputs, 4 Inputs, and 8 bi-directional three-state lines
one open drain output and
high current outputs"

A comparison chart shows it has the same ROM and RAM as the S2150 (1.5KB ROM, 80 nibbles RAM). I don't see any info about the D-to-F or counter/timer registers, though.