O.T. question on MoVs


Hi all,
Somewhat off topic power supply related.
I got some MoVs from aliexpress which I ordered to use in series to protect a 277VAC, 90mA mains supply from high transients.

They ought to be a pair of 270VAC units in series, shorted across the 2 wire AC supply from high transients.
07D271 type part. They capacitive coupled design (2.2uf, 450VAC polypropylene Caps on both lines) allow for 900VAC transient operation without issue.
But ..they shipped unmarked and the supplier is not responding. So it seems I need to do a test bed to validate their function.
Any advice on the approach?

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