u/HearingAmbitious2197

Is a droids name (like R2-D2) their model number or their specific identification number? If it is unique to each droid does that mean that each model is one of a kind? Like are there no other R2-D2s? And if his identification is D2 then are there only a couple dozen of his model, as there is only a letter and a number? I would think there would be thousands of identical droids.