In the early 1990's Hammond switched over their
166 family from Canadian to off-shore manufacturing and caused a shitstorm because those parts were really cheap and ran noisy and hot. It caused problems for any manufacturer using them. I flamed Ross Hammond and probably his dad, said if you want a cheap line, instead change the series part number so we aren't duped. He said they made a mistake and had to roll back the assembly and specs.
167's are made in china but to their specs and I find them OK.
Saturation due to primary (line) voltage isn't some sudden happening, it does ramp up.
Here I took an old made in Canada 167M25 115VAC 25VCT 3A 75VA up to 190VAC until it literally leaped off the bench. PF 0.47 at 90VAC input, PF 0.33 at 110VAC (3.3W) (5.8W at 120VAC), PF 0.13 at 145VAC (13.3W).
made in china 166JA12 115VAC 12VCT 1A 12VA, core does do worse. Similar PF 0.333 at 110VAC input.
Neither show any compression of output voltage which I expected. The primary current (magnetization) waveform is always ugly, sharp distorted peak not a sine wave at all and need true RMS to measure it.
The problem is the transformers have old 115VAC design/spec yet are getting 125VAC, so they waste several watts at lo load and there is no "eco" spec or product line that I know of.