And give us the series marking and number on the sides of the receiver as well, that speaks volumes, and might narrow your production date down some.
The other thing is show or talk to us about the bolt handles, the safety knob, sights, buttplate, cleaning rod(s), all can tell us a lot more about the rifle.
The Type 99 probably underwent more changes in it's relatively short lifetime than any other contemporary military rifle, while they made about 2.5 million of them in that time frame, there are so many differences it is sometimes difficult to see two that are EXACTLY alike which adds a little fun to collecting them.
And they are definitely escalating in price to collectors, a FAR cry from even 20 years ago when it was not uncommon to find them available for $20-$25
GOSH I wish I knew then what I know NOW, but then again, that's the story not only of MY life but many others too!