Some thoughts based on stuff I've seen (this is a hobby, I am not a pro). All comments assume this is audio stuff.
1. Sometimes an output transformer will have COM, 8, 16 near one set of windings - usually means 8 or 16 ohms and my experience is related to vacuum tube/valve amp. It tells you nothing about the primary but you can work backward and apply small AC voltage to the secondary -then measure the primary to get a turns ratio.
2. Usually the driver transformer will be smaller and neither the primary nor the secondary will be low impedances (like 8 ohms or 16 ohms).
3. For a time, solid state audio amps made use of transformers between stages and at the output. I've wondered if this wasn't a carryover from vacuum tube days - then designers eventually found a way to live without them. Typically the drivers were smaller - though for solid state stuff I've only seen transformers on relatively low power amps - a watt or two at most.