There's a good chance the Ademco 216 & 215 can be used with your system. I can't say for sure without being able to examine your equipment, but I'd guess that the mini-PCB above your control panel is the adapter/interface between your panel and keypad. I would also guess that it's capable of supporting more than the one keypad you have, but that's beside the point.
Just FYI, the 215 display is one red LED with 4 modes: Dark (Not ready to arm, _or_ system inactive), slow blink (disarmed, ready to arm), solid/steady light (Armed), rapid blinking (system in alarm). As with your current system, the code is set in the adapter with jumper wires. Code cannot be read from keypad, a weakness of some of the old generic keypads.
If you meter the connections between the mini-PCB and main panel, you will probably find a pair (pins or wires, whatever it uses) that reads some voltage that drops out momentarily when the right code is used at the keypad. That would tell you where to wire the two corresponding wires of the Ademco 216. I don't remember off the top of my head how many wires the 216 has, it might be 8, but you'd have to determine what function each of your existing wires serves, to find its corresponding wire on the 216. For example, probably one wire, "A", signals "Ready to Arm", another "B" signals "Armed", another may signal system in alarm, etc.
Also, the 216 comes in 6VDC and 12VDC (216-12) models--it matters what voltage your CP (control panel) supplies to its adapter/interface. A peculiarity of some adapters and keypads in the alarm industry is that the Red wire, usually reserved for DC Power, can be anything---sometimes the blue wire was used for keypad/adapter power, so don't make assumptions.
Wish I could be more help, but without a ;manual I'm kind'a shooting in the dark.