However, the TR-707A is indeed a rare model, please start your own thread for it, many here including me will be interested to see pictures - and how you get on with working on it.
We have 10 examples of the TR-707A on file in the database. They were manufactured between December 1965 and August 1967. Please post your serial number and I'll add it to the database. The more serial numbers we collect, the more accurate this "range of production" information becomes.