Imperial Russian gold had three standards in zolotnik: 56, 72 and 92.
Pure gold is 96 zolotnik, so it is easy to calculate from the equation 96 = 1000: the value of 56 is 583.3 or 14K, 72 is 750 or 18K and 92 is 958.3 or 23K.
In short, 58 was not gold standard.(Theoretically, it would be 610.5 or 14.7 K, a non existing gold standard).
For a short period after the revolution there were lower standards expressed in millesimal units (375 and 500).
In conclusion, there was well established system of makings in Russian Empire,including standards and shape of the marks, assay offices and maker`s mark, I see no connection whatsoever between marks shown in this post and Imperial Russian marks.
In regard of your marks I would test it having in mind the possibility of gold plating and rolled gold.