This particular rifle was made at Nagoya arsenal during the sixth production series, or about halfway through the overall production of Type 99s there. It's impossible to date Arisaka manufacture, though, as all the records were destroyed by American bombing.
Basically, the first symbol on the side of the receiver is the series mark, the arabic numbers are the serial number (each series ended at #99,999), and the final symbol is the arsenal mark.
The lack of wings on the rear sight is probably correct and how the gun was made, as the AA wings were dropped form production fairly early on. It's too bad the stock was chopped down, as that pretty much kills the collector value on what otherwise would be a nice example of an Arisaka. If you do try to restore it, you'll need a new stock, upper handguard, rear sling swivel, front and rear bands, and cleaning rod - and all of those parts changed over the course of production, so you'll need the correct variant of each one.
