When was the submersible dolphin 3K made?

There is no known submersible called "Dolphin 3K". It is possible you are mistaken about the name or that it is a lesser-known submersible.

To help me find the information you are looking for, please provide more details about the submersible, such as:

* Manufacturer: Who built the submersible?

* Purpose: What is it used for (research, exploration, tourism, etc.)?

* Any other information: Any other details you can remember about it, such as its size, depth rating, or any distinctive features.

With more information, I can try to find the correct name and its production date.