Answer

The device that was discovered is a TX Matrix. The TX Matrix consists of one switch card chassis (SCC) and up to four line card chassis(LCC0-4- each one being a T-640). The entire setup behaves like a huge router with the SCC being central, and each LCC can operate as a separate router when it is not part of a matrix. This behavior is normal and also a similar matrix is displayed while discovery of T-1600s.