Seals and stamps, as well as their impressions, have been the objects of forensic identification for many decades, and although there are legal grounds for refusing to use seals by economic entities at present, documents are still certified with seal impressions. Recently, a great number of documents have been received for examination to address the issues as to the time period for document production. The forensic task on establishing the time period for document production is relevant.
Only in the 80-s of the last century research regarding the possibilities of determining the time period for document production by impressions made by seals (stamps) clichés, produced with the help of vulcanizing rubber using movable types or typewriter composition was initiated. Over the past forty years, cliché manufacturing processes and the materials used in this process have significantly changed. At present, clichés produced with the use of new technologies are widespread, namely: laser engraving of rubber made by using photopolymer technology or flash technology. Changes in the technology of making clichés, production of new materials have led to the emergence of features that are formed in the cliché while its using. These features are displayed in the impressions of seals and stamps clichés. The article outlines the characteristic features of seals (stamps )clichés, considers the conditions for the occurrence of features in the process of their use, shows the evolution of their change, outlines the time periods for the existence of features, defines the criteria for attributing features to identically significant temporal features of the cliché. The mentioned temporal features appearing in the cliché of seals and stamps in general (taking into account handles) and in impressions over a certain period of time, allows to determine the time period of applying the impression on a document. In this case, free samples of impressions that have been made over the time period of examination and meet certain requirements should be provided for comparative analysis.
For the categorical conclusion that the impression of a seal (stamp) was made in a specific period of time, it is needed to establish a set of persistent individual features that appeared in the studied impression and its copy over a certain period of time.
