Indeed a good-looking bunch...
Орден "Народна Република България" - instituted on 18 June 1947 and awarded to Bulgarians and foreigners for services connected with the defence, freedom and independence of the Republic, and in wartime to officers of the Bulgarian People's Army for outstanding leadership and operational planning.
The ssecond and third classes are identical in appearance, the difference is only in the size - the second class is 44x42mm, the third class 40x38mm.
There are actually 2 types, the difference is in the layout of the state arms on the obverse:
Type 1: 3 bands connecting the ears of wheat with the inscription 9.IX.1944 on the bottom band.
Type 2: 4 bands, 2 to each side, with dates on the bottom ones, 681 to the left and 1944 to the right.
Not sure when they changed it, though. Yours are all Type 2.
The first award, on the very day it was created, was to Georgi Dimitrov.
Here's a First Class Type 1 for comparison: