There are a few things to be clear here. You have 10Ω and 42Ω. I assume it is rather DCR of the Pri and Sec. Doesn't tell you much--often those wound with different wire diameters...

Then you measured 1:1.3 voltage ratio--already much better. Once you know inductance of one of the Pri then it gives you much better idea what's going on. Say, you assume -3dB at 30Hz and measure Pri inductance as 1H. Then from the equation:

L = X / ( 2 × π × f ) Where X is impedance and f is frequency (another way of thinking about it is the low end response of the transformer is its inductance for given low end response)

you find that

X= 1Hx (2 × π × 30Hz )=188.4Ω (so in this case you would have a 200Ω transformer, which is pretty close)

Your Sec impedance is 188.4Ωx1.69=318.4Ω

Of course, your Pri inductance will be different. Once you are able to measure it you will know exactly what your transformer is.

Best, M