Yup, Vuelta inner chainring, 38 or 39. I have those too. Very good quality, equivalent to my Shimano and Suntour chainrings.

I've also using a 52T Biopace big ring and 38 or 39 Vuelta small ring for awhile last year. But I switched back to the 42T Biopace, which feels subjectively like a 39T ring to me due to the effect of the eccentric ring shape.

Currently my Ironman has a Vuelta SE Plus ramped and pinned 50T big ring and 38T plain Vuelta small ring. Works great for our terrain and my mediocre legs. Better on climbs and I mostly coast down the steeper downhills.