BAD IDEA!...........COOTIES!!
Just kidding.
..... I own a few Brooks saddle I bought used and I haven't had any problems with them, but maybe because the ones I bought used, were in very close to new condition. Well used Brooks saddkes though can be a problem with fit and comfort as they had already confirmed to the shape of the previous owner that might nit fit you, plus it might have been treated with enough wrong substances that could lead to its premature deterioration.
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72 Line Seeker
83 Davidson Signature
84 Peugeot PSV
84 Peugeot PY10FC
84 Gitane Tour de France.
85 Vitus Plus Carbone 7
86 ALAN Record Carbonio
86 Medici Aerodynamic (Project)
88 Pinarello Montello
89 Bottecchia Professional Chorus SL
95 Trek 5500 OCLV (Project)