"Venetian" and "Oil Rubbed" are old art terms that describe the addition of polished highlights to aged (oxidized) statuary bronze that turns a rich red brown color because of it's 90% copper content. Brass normally contains about 70% copper.

Since copper is expensive and it takes a long time for bronze to darken naturally, modern manufacturers take some short cuts in the factory.

The cheapest simulated aged bronze finish is paint.

Next is the chemically accelerated oxidation of brass plating.

Next is the chemically accelerated oxidation of solid brass.

Next is the chemically accelerated oxidation of copper plating on solid brass (probably the best compromise of cost and quality).

Top of the line is the chemically accelerated oxidation of high copper content cast bronze.

It is very difficult to get reliable information from manufacturers about how they achieve an ORB or Venetian Bronze finish so be careful and be prepared for a finish that not only wears unpredictably but may be difficult to touch up or refinish.

directdoorhardware.com might be worth a try although I don't know how they compare price-wise

Usually, the only way you can determine the materials, the method of finish and the performance grade is to look for the ANSI/BHMA product number. Unfortunately, you will need ANSI/BHMA standard 156.18 to decipher it, but any architect or door/cabinet hardware store should have a copy of it.