an ad for...

[Itasan]

"a magazine advertisement for watches"
Is it an ad that wants to sell watches or
that wants to buy watches?
How about:
1. an advertisement of watches
2. an advertisement about watches
Thank you.

[fluffyhamster]

If people want something, the advertisment often says something like 'Watches wanted - cash paid!'. 'A magazine ad for watches' would therefore normally be interpreted as meaning 'an ad to make consumers aware of the new product, and tempt them to buy it'. As for 'selling', well, this type of big glossy ad certainly "sells" the product, but again, it is not strictly "an ad to sell a watch" - for that, we could say something like, 'Rolex watch, as new, $300 o.n.o'.

Generally, there is a specific type of wording associated with CLASSIFIED adverts/columns, and private individuals usually will follow the accepted style in writing their own classifieds. To talk of 'a magazine ad for watches/Rolexes' would make most people think it is an (magazine) advertisment rather than a classified (advertisement) (what I'm trying to say is that rather than have differing collocates in relation to 'advertisment', you could treat or think of 'advertisment' and 'classified' as two separate words).

[Itasan]

Thank you very much for the detailed explanation.
"an advertisement FOR watches"
Do you say 'an advertisement OF/ABOUT watches' also?
Itasan

[fluffyhamster]

I was implying before that using 'for' is the most idiomatic choice. 'Of' and 'about' are much less acceptable to my mind (but doubtless some contexts could be found where such usages might be appropriate).

By the way, don't forget that one could always be more specific with modifiers: An ad for Rolex watches, or A Rolex ad.