These model kits were made by Academy in Korea. The copyright is 1986, but I don't know if that is when they were actually made. Supposedly there is a release of these by a company called DaiWon, but I haven't seen packaging that says DaiWon, and I speculate that it's an incorrect statement somebody made, and it spread throughout the internet as being factual... but is not... . DBZ Wikia even attributes the model kits to DaiWon, but every one I've ever seen clearly has the Academy logo.
They have absolutely the coolest packaging artwork of any DB/Z/GT item I know of. Absolutely beautiful. The models come in sheets of plastic and you have to snap them off, build them, and paint them if you wish. They come with stickers, and even in mint condition, they honestly do not stick all that well! Yamcha and Tien are 6.5 inches tall, so these kits are quite large scale. A lot larger scale than the Irwin model kits, Bandai Full Action Kits, and AB model kits. They blend in pretty well with the size of some of the IF Labs DB figures.
Dragon Ball Z model kits
Academy also rereleased the Bandai Battle Z sets. The packaging on these was not as impressive as the DB kits, but the packaging is different from the Bandai packaging, which is neat. You can see one of the Academy ones in detail here: blog.naver.com/artgihun/20181171857 I don't know when these were released. The original Bandai Battle Z sets were released in 1992 based on the one I own. The average character in these sets is about 3.5 inches tall. They come with stickers that do not stick well, and you are better off painting the characters.
The picture below is of both Bandai sets. This pic is just here so you can compare the packaging to the Academy versions above.
Here's a group pic of the models. I've painted Umigame (turtle), Puar, Oolong, Chaozu, and Tien.
These look freaking awesome together. If these were more readily available, I would totally collect them all. The scale is pretty nice, as well. The bright colours are just so eye-catching. I love your paint job on Chiaotzu! Tien's skin looks really nice, too.
Yamcha's head in Bulma's hands is kind of terrifying, though.