EFKE 'F' 'K' (FotoKemika, Yugoslavia) licensed the old Adox (Germany) formulas after Adox went out of business and sold their coating equipment to duPont to coat litho film. In other words, Efke 25 is the same product as the old Adox KB14. KB is German for 'Kleinbild' or what in English is 'miniature' or 35mm film. '14' is the old DIN speed number. KB14 was ASA20, not 25. KB17 was ASA 40, and KB21 was ASA100. I used all of these films 35 years ago. The only one worth a damn was KB14. The 40 speed and 100 speed films were very grainy for their speeds, and KB14 was not as sharp as Panatomic-X, though slightly finer-grained than the Kodak film. I quit using KB14 after a few years and starting using Ilford FP4 much more when it came out in 1969. The old DIN numbers are now the degrees in the ISO speeds.

14=20 (Adox KB14)
15=25 (Kodachrome II)
16=32 (Panatomic-X after 1964)
17=40 (Panatomic-X before 1964)
18=50/64 (Agfachrome CT18)
20=100 (Adox KB21)