Vietnam today is normally seen as an assembly workshop. But in the past (before 1990), when VIetnam, like other Eastern bloc countries, focused on heavy industry, we manufactured indigenously quite a lot. Some example:
1. Semiconductors: the first transistor was made in Vietnam in lab by professor Dam Trung Don (the uncle of the physicist Dam Thanh Son) in Hanoi in 1964. And from 1979 to 1990, until the collapse of the Eastern Bloc, the Z181 factory (based in Hanoi) manufactured and exported transistors and diodes, the basic components of computer to the Soviet Union and other countries.
2. Diesel engine: Before 1990, Vietnam manufactured thousands of diesel engines every year for agricultural tractors and other applications. The Song Cong diesel factory (based in Thai Nguyen province, around 40 km from Hanoi), founded in 1960s, manufactured diesel engine upto 55 HP

The D50L diesel engine (55HP) manufactued in Song Cong factory (Courtesy from its website). Every year, the factory produced 600 pcs. of this engine, until the wave of Chinese and Japanese engine imports made it to stop.
3. Machine tools: Vietnam today has to import nearly all of machine tools for industry. But back in late 1950s to early 1990s, the Machine Tools Manufacturing Factory No.1 (based in Hanoi) started to produce various machine tools, including lathe, milling, drilling machines etc. and they were used in almost all mechanical workshops countrywide and even exported. Some components might still be imported from the Soviet Union and other countries.

The ubiquitous lathe T6M16, manufactured by Machine Tools Manufacturing Factory No.1

The T616 lathe manufactured in 1958. In the copper nameplate, one still can see "Nha may co khi Ha Noi" (Hanoi mechanical factory, its former name)