Need help identifying an old Crosman

Does anyone know what model this old Crosman is? It belongs to a friend and has no model#, just the Crosman logo. Any info would be appreciated! 

Thanks,

Todd

Crosman 101 CG (compressed gas). The original tanks were from life rafts.

 I have no idea of the veracity of the following, but the question of caliber stands out as an important detail.

From here, https://ricksshop1.blogspot.com/2013/10/the-crosman-101-my-favorite-air-gun.html

"Crosman first introduced America to "CG" Compressed Gas (CO2) in 1931 at Camp Perry. Development of this new technology was interrupted by WW2 and was put on hold. Production of CO2 air guns was restarted in 1946. These air guns were not for sale to the public but were made available to commercial shooting galleries. In 1947 Crosman opened a new division, Rifle Range Inc. to market modern indoor rifle ranges to shooting clubs, veterans organizations, YMCAs' and schools. 

The CG air guns were eventually made available to the public, the CG guns were divided into two classes, commercial and noncommercial. The commercial guns were made in a unique .21 caliber,  ammo was only available for these air guns from Crosman.

All of the Silent Rifles, models 100 thru 104 were modified into the CG configuration and were available for non-commercial sales."

as you can read on the 2nd page they were available also in .177 (rare) and .22 (common)

Thanks for the replies, the owner was thrilled to finally find out what he has! He is looking for a peep sight for it, and I know it's a long shot but if anyone knows of a source for something like that please let me know and I'll pass the info along to him.

Todd

https://www.jgairguns.biz/100-and-101-pump-rifles-c-78_89_95/