Yep, rulers missing.
Looks like your autofocus plunger is absent too.
The amount of corrosion on there & the replaced(/repainted?) I-beam cover screams PVC.
This could well be the reason for the missing parts, I've seen what PVC does & it ain't pretty!
Hopefully you can get this back to a satisfactory condition without too much expense.
Try a dremel for attacking the corrosion, with a buffing wheel & metal-polish.
Also, Don't waste the money on the auto focus plunger. Many of us have removed them on purpose.
Steve I am sure will sell you one if you really want, but at his suggestion, I removed mine and now focus manually only.
Steve is a good guy and will be very helpful
Jim Watkins
Aliso Viejo, CA.
EPILOG Mini 24 - 45w
Corel X4; PhotoGrave 3.0
Nova 1624-44 Lathe