There are a couple of different models of takedown rifle, as well as versions of the Type 38 carbine with folding stocks. There were experimental versions, but the main takedown rifles were the Type 100 and the Type 2. They were all intended for paratroops, not spies or snipers.
Type 100 (Year 2600 - 1940) rifles were modified Type 99 (Year 2599) rifles and are marked Type 99. They did suffer from loosening at the joint after about 2000 rounds. Accuracy should not have been affected, as both sights are on the barrel. Some writers suggest that perhaps 75,000 were made, but there probably weren't that many.
The Type 2 (Year 2602) takedown rifles , were purpose built and marked Type 2. They have a stronger joint and were made apparently through the end of the war. They were serial numbered in their own series and the total would seem to be 21223.