As the adjustable 5A regulator LM338K is usually sold for around 100 currency units, anything well below this figure will very likely be a counterfeit part. I got some with a troubleshooting job and could not resist to check them.

While the printing already looks fishy, it seems to be what it claims to be, it behaves like any LM317/350/338 type regulator under low load. But when increasing the load, it quickly became clear that it is not a 338 as the current remained well below 2A and then suddenly dropped to zero.

So I opened up another specimen and had a quick look through a microscope – the die clearly says 317 (no photo made, sorry). But it does not even fullfil LM317K specs, here is the opened device running at around 0.9A