There's a whole lot happening in here. In addition to the ferrite bar antenna for AM reception, AM external antenna jack, and metre-long telescoping rod antenna for FM reception, there are also two large nuts above the left battery holder to which the user can attach a TV antenna as an FM external antenna. Another feature is the "line-in" and "line-out" connectors that allow one to hook up a record player or other sound equipment.
The 4" x 6" oval speaker is not the only component shared with the TR-74 and TR-741. As with its AM/SW siblings, the telescoping rod antenna on the TFM-151 does not tilt or swivel. This means when not connected to an FM external antenna, the TFM-151 could also be found in a "reclined" position on its handle as the user rotated the entire radio to achieve optimum reception when listening to FM.
Transistors: 2T203 x 3, 2T201 x 5, 2T76 x 2, 2T65 x 3, 2T85 x 2, [1T23 x 4, 1T51]
Power source: 4 x D-cells (UM-1) = 6V
AM band: 535 ~ 1605 KC
FM band: 88 ~ 108 MC
The photo above shows the second earliest serial number I have seen to date. It was common during this period for Sony to begin models at number "1000" or "10000", so this is possibly the 154th unit off the production line. The earliest serial number I've seen so far is 1129*, and latest is number 2247**. Of course, I remain more than happy to revise this information if and when any kind soul cares to share information with us on a TFM-151 sample that has a serial number outside of this confirmed range. (Photos of the sample would be most appreciated, including one that shows the serial number.)
Note also in this photo that the circuit board is the earliest type marked "010-6". The board was revised to the "010-6A" version by the time production reached serial number 1439.
The early unit pictured above also differs from later production in that it continues to use the plain rectangular label common to the TR-74 and TR-741 with the early Sony logo to the right of the serial number. The label changed to a smaller one with serrated edges, (as though cut by pinking shears), by the time s/n 1439 was produced. You can see the later serial label in the photo at the top of this page, (the photo showing the insides of the unit with s/n 1599).
* While the above image of a pre-production prototype unit taken from the first pamphlet Sony printed to introduce the TFM-151 in late 1958 doesn't prove anything, it could be read to suggest that Sony may have pondered starting the serial number series for the model at "10000" instead of "1000".
* [07.04.15]: Many thanks to Steve Poroszlay and Michael Jack for contributing and expanding the range of serial numbers in my database. Steve's information now spreads the range by a whopping 25 units on the early end, (from s/n 1154 down to 1129), and Michael's by 13 units on the high end, (from s/n 2153 all the way up to 2166.)
** [08.09.14]: Special thanks to Dr. Grigorios Angelidis of Athens, Greece for taking the time to write in and share information and photos on his TFM-151. Carrying the serial number 2192, his sample expanded the known range on the high (late) end a further 26 units.
** [13.02.13]: Special thanks to Tom Courtney for writing in and sharing a photo of the circuit board from his TFM-151. Carrying serial number 2231, Tom's sample extended the known range on the high (late) end a further 39 (possible) units.
** [16.06.11]: Heartfelt thanks to Shaun Poole for contributing data on his TFM-151 samples, along with photos for confirmation. One of his two radios sports the serial number 2247, extending the upper range by 16 and bringing the total of *possible* production to about 1,118 units. (It's impossible to say with certainty whether Sony actually shipped radios that would account for all the serial numbers issued for the model.)