There are a few socketed Chips.

On the CPU daughter board with RE-232-C ports and the battery there are 2 with ICs and one with out an IC


U41 has a sticker of 827.8767 and is near the mother/daughter socket.

U25 which is double the the width of the first with 827.9268

U13, a socket the same size as U41 is empty.

There is only only on the main board, but the daughter board is blocking me from reading it. It looks like it reads U40

Do you want me to remove the daughter board?

Also the part number of the CPU daughter board is "silk-screened" 550.2023.
The Mother CPU board is
"screened" 550.2026 V
826.4064-9 (AB sticker)

But the sticker on the aluminum bracket near the fiber optic port reads
550.9035 AU

Does that help?