Krause lists:
P-234a Lilac tinted paper, no UV activity
P-234b White paper, /w UV activity
P-234s Specimen
Russian catalogs give more detailed breakdowns:
Paper type 1: plain lilac-tinted paper
Paper type 2: glossy bright white paper
Paper type 1. No UV activity. Series АА-ББ.
Paper type 1. No UV activity. Special (experimental/replacement?) series ЯА or ЯВ.
Paper type 2. No UV activity, series ББ-ЛК.
Paper type 2. No UV activity, series Аа-Лх or Пп-См (series Лч-По were not printed).
Paper type 2. UV activity, w/ ultraviolet stamp "25 РУБЛЕЙ" with violet/light-blue colored frame around it. Series ЛЛ-ЭЯ.
Paper type 2. UV activity, w/ ultraviolet stamp "25 РУБЛЕЙ" with yellow/greenish colored frame around it. Series Аа-Лх or Пп-См (series Лч-По were not printed).
Plus specimens:
- Separate front and back single-sided w/ diagonal overprint (in red or black) "ОБРАЗЕЦ" and serial number АА 0000000
- Double-sided, perforated horizontally "ОБРАЗЕЦ", without a serial number
Sources:
http://fox-notes.ru/img_rus/USSR_1961_25_RUB_D030717A.htm
https://moneta-russia.ru/paper/bumazhnye-25-rubley-1961-goda-tsena.php
https://www.russian-money.ru/banknotes/sssr/1961-1992/25-rublej-1961--211
http://shopcoins.narod.ru/25_1961_1BB.html
ps: As far as I can tell, there is no small,small variety, so it should probably be removed.