Hello Ashley,
Over the years there were several so called direct replacements for the VF14 that all claimed to be identical, most build upon the Western Electric 40x series, either the 20/40 V version of the 2C51 (407) or the 50mA/20V version of the EF95 (408).
Depending on the maker (WE, NE, GE, RCA, Ericson, Philips) some of them sound O.K. but have nothing to do with an VF14. Some other tubes that are favored, were the 5904 to 5908 group of tubes, but none of the above is really a direct replacement.
Passing signal does not mean it sounds good and there are a lot of people whom I meet that love the sound of the 5905, mostly in conjunction with a Thiersch reskin.
If one of the guys posting here really uses this forum to try to discredit you, I think Klaus would take care of that.
Regarding your claim of a custom made tube, I do understand to keep the real designation under wraps, in case it would sound the same as an VF14, but all tubes, whether of western or eastern origin are quite well documented and none has an ML designation. The Brits used CV for custom valves, the Americans STR; so what is up with your 'ML'? Are those ones custom made for you?