The Toneking alto and tenor switched over to the "Superba Style" keywork at almost exactly s/n 68000.
The baritone switched to the new keywork and new bell-to-body brace at about between 83602 and 88xxx.
The straight Bb soprano may not have changed until the SX90 came out, around s/n 99000 (1993).
My (Pete) opinion is that all basses were custom made -- and I've only ever seen one Toneking bass.

Fatal error: Uncaught mysqli_sql_exception: Table './bassicsax_petepiwigo/kah_history' is marked as crashed and last (automatic?) repair failed in /home/bassicsax/public_html/pix/include/dblayer/functions_mysqli.inc.php:132 Stack trace: #0 /home/bassicsax/public_html/pix/include/dblayer/functions_mysqli.inc.php(132): mysqli->query('\nINSERT INTO ka...') #1 /home/bassicsax/public_html/pix/include/functions.inc.php(538): pwg_query('\nINSERT INTO ka...') #2 /home/bassicsax/public_html/pix/index.php(373): pwg_log() #3 {main} thrown in /home/bassicsax/public_html/pix/include/dblayer/functions_mysqli.inc.php on line 132