I was hesitant to use the work "Marketing" since there's so much baggage associated (and lot's is negative) with the word. Many here know that I've used that same word in rather disparagingly terms too

but is it the word/term that Eric used, so I did too. In this context I feel that "marketing" means the distribution of the tubes primarily and the "advertising" less so.
In this context I view Sachs and Serotta both to be marketing brands. Both have at best designed specific to their specs tube sets (and with Sachs associated components for building) then contracted with a tube drawing company to produce said tubes.
Again, in this context I see nothing wrong in this label and this process to get to the market a product. We see this every day in other industries. My local grocery store has their own line of a number of different products (from canned veggies to plastic garbage bags to ready to eat foods). In this effort they do also market (as in advertise, the, sometimes, less then stellar function that this word covers) their products. But that department (and here's some of my point WRT how marketing/advertising is used) also markets/advertises a lot of other products branded by other companies that they also sell. (Much like Nova promotes their house label products and those of Columbus).
So I should have added a qualifier to
'only a marketing company' (that I wrote). The qualifier would read something like "when it comes to their self branded tubes". In no way was I trying to say that they only sell tubes, that these tubes are in anyway inferior to others' tubes or that being in the business of bring to the market an in house designed product but one that is contracted out to produce is a wrong thing. Andy