| Prüfer | Art der Urkunde | Katalog | KatalogNr. |
|---|
| Oechsner, Helmut (BPP (Bund Philatelistischer Prüfer)) | Kurzbefund | Michel | 208 |
| Oechsner, Helmut (BPP (Bund Philatelistischer Prüfer)) | Kurzbefund | Michel | 228 |
| Oechsner, Helmut (BPP (Bund Philatelistischer Prüfer)) | Kurzbefund | Michel | 7 |
| Oechsner, Helmut (BPP (Bund Philatelistischer Prüfer)) | Befund | Michel | 24 Y |
| Oechsner, Helmut (BPP (Bund Philatelistischer Prüfer)) | Attest | Michel | 15 |
| Oechsner, Helmut (BPP (Bund Philatelistischer Prüfer)) | Attest | Michel | 24 X; 29 SZ |
| Oechsner, Helmut (BPP (Bund Philatelistischer Prüfer)) | Attest | Michel | 24 X; 29 SZ |
| Oechsner, Helmut (BPP (Bund Philatelistischer Prüfer)) | Attest | Michel | 26 II |
| Oechsner, Helmut (BPP (Bund Philatelistischer Prüfer)) | Attest | Michel | P 26 II |
| Oechsner, Helmut (BPP (Bund Philatelistischer Prüfer)) | Attest | Michel | P 28 II |
| Oesch, Herbert (Sonstiges) | Attest | Michel | 17 Bx |
| Okday, Ismail Hakki (Sonstiges) | Befund | Michel | TR |
| Oliva, Guglielmo (Sonstiges) | Attest | Michel | 4 |
| Oliva, Guglielmo (Sonstiges) | Attest | Michel | 10 A |
| Oliva, Guglielmo (Sonstiges) | Attest | Michel | 4 a |
| Oliva, Guglielmo (Sonstiges) | Sonstiges | Michel | 3 I |
| Oliva, Guglielmo (Sonstiges) | Attest | Michel | 1 - 12 + 13 - 15 |
| Oliva-Savarese, Bruno (Sonstiges) | Attest | Michel | 1 |
| Onofri, Mario (AIEP (Association internationale des experts en philatélie)) | Attest | Michel | |
| Opitz, Walter (BPP (Bund Philatelistischer Prüfer)) | Attest | Michel | 1 a |
| Opitz, Walter (BPP (Bund Philatelistischer Prüfer)) | Attest | Michel | 18 |
| Orbán, Ferenc (Sonstiges) | Attest | Michel | 8 a H |
| Orlandini, Fabio (Sonstiges) | Attest | Michel | 628 b |
| Orlandini, Fabio (Sonstiges) | Attest | Michel | 661 - 663 |
| Orlandini, Fabio (Sonstiges) | Attest | Michel | 834 - 836 |
| Orlandini, Fabio (Sonstiges) | Attest | Michel | 834 - 836 |
| Orlandini, Fabio (Sonstiges) | Attest | Michel | 89 |
| Osper, Horst (BPP (Bund Philatelistischer Prüfer)) | Attest | Michel | 1 |
| Osper, Horst (BPP (Bund Philatelistischer Prüfer)) | Attest | Michel | 13 |
| Osper, Horst (BPP (Bund Philatelistischer Prüfer)) | Attest | Michel | 512; 662; 668; 669; 672 |
| Osper, Horst (BPP (Bund Philatelistischer Prüfer)) | Attest | Michel | 13; 13 I |
| Osper, Horst (BPP (Bund Philatelistischer Prüfer)) | Attest | Michel | 15; 15 I |
| Osper, Horst (BPP (Bund Philatelistischer Prüfer)) | Befund | Michel | 19 |
| Osper, Horst (BPP (Bund Philatelistischer Prüfer)) | Befund | Michel | 19 I |
| Osper, Horst (BPP (Bund Philatelistischer Prüfer)) | Attest | Michel | 48 |
| Osper, Horst (BPP (Bund Philatelistischer Prüfer)) | Attest | Michel | 48 Zf w |
| Osper, Horst (BPP (Bund Philatelistischer Prüfer)) | Befund | Michel | 4 |
| Osper, Horst (Sonstiges) | Attest | Michel | 4 a |
| Osper, Horst (Sonstiges) | Attest | Michel | 45; 46 |
| Osper, Horst (Sonstiges) | Attest | Michel | 131 Lw |
| Osper, Horst (Sonstiges) | Attest | Michel | 2 |
| Osper, Horst (Sonstiges) | Attest | Michel | 31 F + 34 F |
| Osper, Horst (Sonstiges) | Attest | Michel | B 665; 1063; 1066; 1150 |
| Osper, Horst (Sonstiges) | Attest | Michel | 1224; 1226; 1227; 1229 |
| Osper, Horst (Sonstiges) | Attest | Michel | 16 III |
| Osper, Horst (Sonstiges) | Attest | Michel | 171 C |
| Ossa, Mikko (Sonstiges) | Attest | Michel | 2 z |
| Ossa, Mikko (Sonstiges) | Attest | Michel | 3 a |
| Ossa, Mikko (Sonstiges) | Attest | Michel | 3 A |
| Ossa, Mikko (Sonstiges) | Attest | Michel | 3 A |
