Number | Name | Date | Kind |
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4286325 | Dlugos et al. | Aug 1981 | |
4301507 | Soderberg et al. | Nov 1981 | |
4466079 | Daniels et al. | Aug 1984 |
Entry |
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Torrance et al., European patent application EP0019515A2, "Electronic Postage Meter Having Improved Security and Fault Tolerance Features". |