The phrase "OFFERED HERE FOR SALE..." has been in so many fraudulent responses to WTB ads that it should be considered a good indication of an attempted scam.
If I saw that phrase in the first few lines of a response, I'd immediately trash the response.
If someone purporting to be a U.S. ham uses that phrase, RUN FAST! It's not an Americanism!!! And it's not something that a foreigner trying to assimilate himself or herself would say!
No, it isn't an "Americanism" as such, but it is how more cultured and civilized people--such as from old England--would speak. Try listening to an auction from an antiques dealer, or from an expensive auction house (Sotheby's, for example) and you would hear such expressions all the time. Offered here, offered here for your consideration, offered here as an example, etc.
In short, just because you hear phrases and terminology that sounds strange to you, don't criticize lest you be classed as an uncouth ruffian yourself! (The last was said in jest.)