While I’m not absolutely certain about the transformers, I’m pretty sure that the channel design was the same as the 828…. yes, it most likely has transformers, and the mixing system is likely to be the same also. This was a very successful design, they were used extensively for commercial production in radio stations all over the world.
The mixer that was less successful was the Itam 10-4. We developed that as an ‘improvement’ over the 828, but it was a poor performer, with sub-standard solid-state mic amps and a noisy mixing system….. It was a good example of ‘Improvement means deterioration’!
If the old 12-48 is in good working condition, it will sound good, and would do a good job as a small mixdown desk. It’s potentially on a par with the better ‘Soundcraft’ small mixers.