The Arnold and Svenson sub-types of Kyiv I Tridents are rarely seen and hard to distinguish. Seichter lists Arnold Type, Type I a 1 (Svenson), Type I a 2 (Svenson) and Type Ib (Svenson). Bulat follows this at pages 12 - 14 of his Catalog.
Seichter has bad illustrations but describes Ib (Bulat's B1)as having a "langer Schwanz" (longer spike / longer prong). This is correct. Unfortunately, Bulat's illustrations for A2 and B1 are the WRONG WAY ROUND (transposed)which caused me real problems until I went back to Seichter.
Anyway, here's a quick Guide:
ARNOLD: normally in standard Kyiv I violet but in green on the 50 kopeck perforated and in both violet and black on the 1 rouble imperforate. Look for the MISSING BASE CAP. Row 1 on my Scan should make it clear. The pair of 1 rouble appears postally used at Zhitomir
SVENSON A1: always violet-black and in my experience ALWAYS placed at the top of the stamp. Found on values unlisted by Seichter or Bulat: see the 35 kop imperforate at the end of Row 2 (ex Zelonka)
SVENSON A2: always in black. Look for the spike ending more or less level with the top of the wings. See Row 3 of the scan.
SVENSON B1: normally in the same black, but look for the spike extending above the wings. Only one value is common to both A2 and B1, the 10 kopeck, and I have put the example I have in the wrong row. You should now be able to see why it should be in Row 4 not Row 3.
One value, the 5 kopeck imperforate, is found with B1 in violet-black and it is shown in Row 5 of my scan.