Section 5.2.1 is a list of documents which may be requested by the consulate when deciding on a visa application, I don't see the relevance to this question. OP already has a visa, the question is whether they can use it to visit a friend.

@ChrisH That list shows that the visa is a form of a transit visa. Thus the purpose is to transit and not to visit. That is relevant to the question.

no, it shows which documents are likely to be requested. Nobody disputes that a seafarer's visa is primarily issued to allow the person to travel to/from a ship. That says nothing about whether or not they can subsequently be used within their validity period for other purposes which are also permitted under type C Schengen visas.

@ChrisH If the C-Visa is issued only as transit visa, it cannot be used as a visitor visa. The quoted text from the visa code shows the the purpose of a seamans visa is for transit. The second uses the word explicitly, the first shows that from entry poit to exit point at a explicit place and date.

@ChrisH An image of the issued visa would probably show that.

yes, an image would solve it. That's my point. The consulate can choose to issue a wider visa than the one requested. The remarks section on OP's visa should be able to provide the answer to OP's question. A list of documents which may or may not be requested by the consulate can't.

@ChrisH Also the health insurance for a seaman may only cover the transit (as part of his work) and not private travel as a visitor.

@ChrisH A C-Visa may only be used for the purpose for which it was issued. You are claiming otherwise. A visitor's visa may not be used as business visa. Both purposes must be stated in the visa to be used in that way. Zthus the multi choise in the application form.

I'm not claiming otherwise, I'm saying that we don't know what is stated on the visa, and your visa code quotes can't tell us. I'm not disagreeing with your overall answer (that it depends on how the visa was issued), I'm saying that the quotes which makes up more than half of the answer don't actually help answer the question, and this answer would be much clearer without them.

@ChrisH that would lead only to someone writing you are making a claim without giving a varified source.

Nobody is going to demand a source for the claim that visas must be used in accordance with their conditions (and we don't know the conditions of OP's visa, so can't give a yes/no answer), which is all your answer boils down to once the distracting and irrelevant visa code quotes are removed. If you don't want to take that feedback on board, fine, I'm done here. Have a nice day.

@ChrisH I wouldn't be so sure about that. But in this case I think that the clarification that a seamans visa is actually a transit visa is useful. I was surprised to see that it was not an extra type on the visa itself (which up to now I assumed). That is why I would be interested in seeing an image of the issued visa.

Doesn't a type c, mutiple entry visa valid for 1 year considered as a tourist visa. In addition to this, I already used the visa for its purpose because I already have been onboard and in fact already disembark the vessel. I am not applying for a new visa, I'm just inquiring if I can use this visa for my subsequent trip (visit a friend).

@SuperOver No, a C-Visa is a general short term visa and is issued for one or more specific purposes. Which purposes are stated in the 'remarks' portion of the visa sticker and can be different based on which country issued it. Could you upload an image of the sticker (with any personal data blotted out)? That would the best way to exactly what it allows.

In the remarks, some numbers (my alien number I think because my two expired schengen visa have the same numbers too) and below is BNL2

@Mark Johnson that is only what is said on the "remarks" of my visa.

@SuperOver You have a visitor's visa. If issued by the Netherlands, then the numbers is the alien number.

Let us continue this discussion in chat.

The terugkeervisum is entirely irrelevant. It is for residents of the Netherlands who need a visa because of unusual circumstances. See ind.nl/Paginas/Afspraak-aanvragen-terugkeervisum.aspx (in English:ind.nl/en/pages/appointment-for-a-return-visa.aspx).

@phoog Do you know how these 3 countries issue a transit. There is no code for that in the BNL series?

@MarkJohnson I do not. I presume that they issue a regular short-stay visa, presumably with a limited duration of stay, probably with a limited number of entries, and possibly with some free-form annotation in the "remarks" section, or possibly not. Anyway, the only significance of "BNL 2" is that it means "visa issued ex officio," which might mean that the consulate decided on the application without referring it to the "central authorities," or it might mean something else.

Since OP clearly states that he has a type C multiple entry visa, most if not all of this answer is likely irrelevant. Unless limitations are clearly stated in the remarks on the visa, I do not see any obvious reasons why that visa can't be used for a regular, non-work-related visit.