If the piano hasn't been tuned in over a year, finding its age is great, but calling a technician is better. Older Beales require a gentle touch on the tuning hammer to prevent breaking the pins.
Some models have the number on a small plaque or stamped directly onto the wooden ledge under the opened lid. Beale Piano Age Chart beale piano serial number lookup
This is the hardest part. Do not look at the sheet music stand. You need to look . If the piano hasn't been tuned in over