Part III: Slot Machine Cheating · Physical Cheating Methods · #5.20
Mis-Made Bill (Strip Swap)
How it works
An early weakness in bill validators was that some models read only the center of the inserted bill, while others read only the corners. Cheats would cut a half-inch strip from both a $1 bill and a $20 bill, then swap them – inserting the $1 strip into the $20 bill. When inserted into a validator that read the center, the bill would register as $20. They could then use the same two bills to create another mis-made bill with the $1 strip inserted into the $20, targeting a corner-reading validator for another $20 credit. This turned $2 into $40 of credits.
Where it appears
Early-generation bill validators with single-point reading (center-only or corner-only).
On the record
George Joseph noted this was “an awful lot of work to steal $19” but was effective against first-generation bill acceptors. As he documented, “The natural progression of slot operations was to begin accepting cash at the machine,” and with this came new vulnerabilities.
Detection & prevention
The paid halfHow a monitoring room catches mis-made bill (strip swap), and what stops it recurring — written for the desk, not the reader.
Detection · 27 words
Prevention · 34 words
Published as a detection reference for surveillance, compliance and gaming-operations professionals. Thresholds and tuning are set by the property. Nothing here is instruction — the method is described so it can be recognised.