Help identify the IC manufacturer: is it really possible that these ICs from the 60's just made a comeback (К155ИД1)?

The chips that you have are made in Belarus by a company named Integral.

• К155ИД1 1814 :- This is a recently manufactured chip. (i.e. 14th week of 2018).
• К155ИД1 8910 :- This chip is very old (i.e 10th week of 1989).

Link to the site of manufacturer.

Yes, it might be possible that the manufacturer is using a slightly modified architecture based on the previous one for the manufacturing of these new chips

You have К155ИД1 1814 chips made in Belarus see this. Company name is Integral.

К155ИД1 8910 is a very old chip made in 1989. Unfortunately, these old chips are hard to find. The Soviet Union made excellent chips; now you need to carefully verify the modern versions.

Consider the possibility that the chips inside these packages are NOS, from 1989 or whenever, but had been stored as bare dies, and have been bonded and packaged in 2018. Which would make a lot of sense if somebody has a stash of bare dies - you could put them in ROHS-compliant packaging. Coincidentally, the pin finish on these does look rather matte, typical of lead-free components...

Alternatively, the parts might be old stock that someone retested, refurbished, remarked and remarketed in 2018.... there might be the more sinister possibility that they have been just remarked, in order to avoid ROHS-related suspicion :)