The rifle is not a purpose built trainer, but rather a Type 38
that has had the mum removed (professionally) and replaced with a character.
Just stamping the oval ring around the mum is a much more commonly
seen type of mum cancellation.
Not sure of the meaning of the 'circle of ovals'.
Immediately between the circle and the 3 is the Mon-Busho, or Ministry of Education symbol.
That, along with the two circles, not zeros, ahead of the serial number
confirm it is a rifle that was removed from active service. The picture is
just a bit blurry, but the stock looks to be a correct two piece rather than a trainer.
It SHOULD be safe to shoot with regular ammo, but of course a hands on
inspection would be required as with any firearm of that age.
JT