Without access to past postage rates, it is difficult to establish which overprints were for specific internal rates, and which were only for foreign rates.
24-27 are for 3 & 5 rouble rates, which must be internal. 24 used in Minsk 25.2.93, 25 in Zaslavl' 11.3.93 is a surcharge not shown before.
26 is a different USSR relic, used in Bobruisk 5.1.94, and 27 shows four 1r marks which may have been applied successively or at one time, used in Grodna Jan 94.
I also have an example of two 1r marks (as in no 27) uprating a 1r PSE to 3r rate, and an overprint similar to no 15 above for '400' but without the 'KOP' at the foot. This is also on a 1r PSE, making the 5r rate.
24.25.26.27.
The 10r PSE at 28 was issued in June 1993 - I have no others, and no letters charged at only 10 roubles.
In February 1994 the worthless kopeck definitives were surcharged with new values.
The next apparent change in rate is to 30r, shown by this surcharged pair on an internal letter 29.
There is also a 30r PSE overprint, similar to no 21 but narrower. This is on an internal registered letter (18.3.94) with stamps of 30r added (the registration fee being equal to the letter rate).
A 40r overprint on 1r PSE in the style of no 21, used to Ukraine in November 1995 with a 180r adhesive, suggests a 40r rouble rate, but there is no other evidence of this.
A more certain change in rate occurred in 1994 with the issue of a 60r PSE 30 and a 120r registered envelope 32 with pre-printed registration mark at top left 31.
28.29.30.31.32.
Yet another type of surcharge appeared from Gomel in January 1995 33, paying the 60r rate which also seems to be valid to Russia. although other evidence suggests that this rate should be 300r or 600r.
Early in 1995 the internal rate increased to 180r and some stamps of this value were issued, although many of 600, 700 & 1000r had previously appeared.
Later in the year the rate reached 200r with registration an extra 100r. I have a 200r overprint too faint to be shown here, which is a modification of no 15/17: the star at the top is replaced by a dot[.], and 'Poshta' appears at the left and 'Belarus' at the right, with 'RUB' at the foot. The value is vertical. This was used at Vitebsk 28.11.95.
I have recorded no more definitive pre-stamped envelopes for internal use. In 1996, commemorative PSEs for 400r and 800r appeared. The 400r 34 comemmorates the 150th anniversary of the birth of M.V. Rytau
and the 800r 35 the 200th anniversary of the birth of Jan Chachot. [As it is virtually impossible to translate from Belarussian with only a Russian-English dictionary, I can only say that Rytau is associated with Gorki, and Chachot with Navagrudak.]
When inflation is running high, it sometimes happens that rates increase while new stationery and stamps are being printed. My material shows an internal rate of 200r as late as February, and 1000r in October 1996(*): I have no record of internal or external rates of 400 or 800 roubles.
33.34.35.36.37.
In the spring of 1996 inflation compelled the postal authorities to produce stamps with no specific value, so that the purchase price and franking value could be changed after issue. The B overprinted on 1r was issued 28.2.96 with a value of 200 roubles.
The A on 25r was issued 13.3.96 with an initial value of 400r. 38, from March 1996, is evidence of B=200 roubles, while 39 from March 1997, each with a total value of 1000r, is evidence that by then B=500r and A=1000r.
38. 39abc
During 1996 at least two pre-stamped envelopes with the 'A' stamp were issued, although one 'stamp' is dated 1995.
These are shown at 40 (with a 700r stamp), and 40a with 500r (not shown) and 200r stamp, both to Moscow, in July/August 1996. The rate is probably 1100 roubles. 40.40a.
25.
26.
27.
29.
30.
31.
32.
34. 
35. 
36. 
37. 
b 
c 
40a.
