This item is a Vintage System Memory Expansion Board manufactured by Eagle Telephonics, likely for a proprietary private branch exchange (PBX) or a business telephone system from the late 1980s to mid-1990s.
​Technical Breakdown
​The board is densely packed with memory chips, which was a common way to expand the processing or storage capacity of vintage telecommunications equipment.
​Manufacturer: Eagle Telephonics
​Part Number: 102193-1 REV. 1 (visible on the green PCB)
​Key Components: * RAM Chips: The large black chips are Seiko Epson SRM20100LM10. These are 1-Megabit (128K x 8) Static RAM (SRAM) chips.
​Capacity: There are 32 of these chips across both sides of the board. This totals 32 Megabits, or 4 Megabytes of total SRAM—a significant amount of memory for industrial equipment of that era.
​Logic Chips: You can also see 74-series logic chips (like the 74HC138 3-to-8 line decoder) used for address decoding. Not tested