I was comparing the company I work for with another one nearby. My coworker dismissed my comparison with "Ja, die sind aber eine ganz andere Hausnummer".
I reckon it signifies difference, but that is where my understanding ends. What would he try to convey?
If the comparison facts are of significance, both companies are roughly of the same size, field and turnaround. The other company is much older (about 80 years compared to my company's 30) and is more oriented towards high volume manufacturing whereas we do mostly services and tailored manufacturing. The Hausnummer phrase came as a response to me saying the other company having Betriebsrat - we don't have one.