Go to this website, http://stevespages.com/page7b.htm and scroll down to Colt .25 or Colt .25 hammerless and it will give you the manuals with all the instructions on how to disassemble.
.25 Airsoft bbs can be good. Their weight is very good for accuracy and helps for a harder hit from the bbs. However, no bb is good if they are not high polish. Companies like Madbull and Matrix make good .25 bbs.
The COLT website has the answers , not knowing which model you have-that is the best an I have =It showed me how to take mine down Colt's Manufacturing Company LLC > Media / Downloads > Manuals
The stinger p9 is good with .12 gram airsoft BBs or you can use .25 gram bbs but then it will decrease the range.
No such sn in the Colt 25 series
No such sn in the Colt 25 range
Yes, Colt and others made them for Colt
Colt hammerless .25 was made in 1920
No such serial number for a Colt 25 ACP
1917 for the Colt model 1908 hammerless .25
You can download a manual here: http://stevespages.com/pdf/colt_25_hammerless.pdf
If you are speaking about a Colt 1908 hammerless .25 , then it was made in 1917.