Could Defects on a Rubber Stamp be Reproduced on a Duplicated Rubber Stamp?

The examination of stamp impressions has been an integral part of questioned document examination since its inception. Matching in design details and unique defects has proven to be essential factors for rubber stamps and stamp impression examination. In this study, several duplicate stamps were made from various rubber stamp manufacturers in Hong Kong, from the same original stamp impression(s). The objective was to examine the stamp impressions prepared from these duplicated stamp products and compared with each other and to determine whether they could be distinguished from the source stamp impression(s); by comparison of the size and defects deliberated introduced onto the latter. Further consideration of this study was an attempt to create a perfect duplicate stamp from an original stamp impression. The results of the analysis showed that the quality of source stamp impression(s) and scanner device of the stamp manufacturing process, and the knowledge of the stamp manufacturer were critical to the quality and outcome of the duplicated stamp products. It is concluded that although a perfect duplicate stamp could only be made under several essential control conditions, it was still possible to create a duplicate stamp that replicated the features of the original when a high-quality source stamp impression was available.

Organizing a Proficiency Testing Program on Stamp Impressions Examination in Accordance with ISO/IEC 17043 Requirements.

Stamps and stamp impressions examinations are based on matching defects and design details on the questioned and control samples. These examinations are routinely carried out by document examiners around the world. International proficiency tests for questioned documents examination have been available for decades while similar programs specifically focusing on stamp impressions examination are rare. This study reported a recent proficiency testing program on stamp impressions examination organized by an accredited provider in accordance with ISO/IEC 17043 requirements. Twenty-four forensic laboratories registered for the program. Apart from giving details on the design and operation of the program, this study also aimed to provide the limitations and difficulties encountered in sample preparations, homogeneity, and stability tests of the testing materials. Various comments and feedbacks received from the participants, particularly in respect of examination approaches, challenges faced by the participants in forming conclusions and their suggestions for further improvement would be evaluated.