Here you see an original TR-6 brochure from Totsuko that was printed around October 10, 1956. In addition to the spiffy graphics that show how trendy and compact the radio is, the ad copy stresses how economical the long battery life is, how the thin, light form factor makes the TR-6 convenient to use, and also that it is the cheapest radio in the Sony product lineup at the time. Sure enough, it does cost less than the TR-5 and TR-72. And the large copy just below the image of the hand holding the radio reads, "TR-6, THE BEST RADIO IN THE WORLD". Quite the claim, huh?

Because I've mentioned the orthography used for the SONY name in katakana, we can note here that it has changed by October '56 to the longer form "so-ni-i" that remains in use today.