This is a really beautiful example of the air rifle identified as the 17P ("P" for pistol grip) on this Diana catalogue page. It appears to date to the period shortly before WW1.
The build quality of this 4.5mm smoothbored gun is quite unbelievable. Its size makes it a youth or small adult 'rifle' but every inch of it is of fine firearms quality.
The MGR logo on the breech has concentric circles and crossed darts, which appears in the 1911 Alfa catalogue.
It is the gun pictured here: