A Preliminary Study on Stamp Impressions with the Same Placement and Orientation on Reproduced Documents—How Easily can it be Achieved by Deliberately Stamping at the Same Relative Position and Orientation?

Yan Wen Crystal Tan; Hui Ying Yvonne Sim; Chin Chin Lim; Chiew Yung Yang

doi:10.69525/jasqde.268

A Preliminary Study on Stamp Impressions with the Same Placement and Orientation on Reproduced Documents—How Easily can it be Achieved by Deliberately Stamping at the Same Relative Position and Orientation?

Journal of the American Society of Questioned Document Examiners

Volume 23 (2020): Issue 2

By: Yan Wen Crystal Tan, Hui Ying Yvonne Sim, Chin Chin Lim and Chiew Yung Yang

Open Access

|Dec 2020

Figures & Tables

(a) design of the stamp die (b) pre-inked stamp with round housing (c) self-inking stamp with square housing.

Table 1.

Number of stamp impressions made for Set 1 to Set 4.

	Stamp used	Template	Quantity
SET 1	Pre-inked stamp	With signatory line	100
SET 2	Self-inking stamp	100
SET 3	Pre-inked stamp	Without signatory line	50
SET 4	Self-inking stamp	50

Table 2.

Alignment guidelines for making stamp impressions.

	Alignment guidelines	Example
Set 1	The ‘★’ is at the 6 o’clock position. The left side of the round housing is touching the comma. The bottom of the housing is touching the signatory line.
SET 2	The left edge of the square housing is touching the comma. The bottom of the housing is touching the signatory line.
SET 3	The ‘★’ is at the 6 o’clock position. The left side of the round housing is touching the turning point of the bottom stroke in the signature.
Set 4	The left edge of the square housing is touching the comma and the turning point in the bottom stroke of the signature.

Reference points for measurement of X and Y values for Sets 1 and 2 (left), and Sets 3 and 4 (right).

Two stamp impressions with the same placement but different orientations.

Table 3.

Percentage match of relative positioning and orientation of stamp impressions.

	No. of pairs of stamp impressions (%match)
	SET 1 •	SET 2 ■	SET 3 •	SET 4 ■
	With signatory line		Without signatory line
Match in position within +/- 0.01 cm	1191 (24%)	958 (19%)	56 (4.6%)	70 (5.7%)
Exact match in position	159 (3.2%)	151 (3.1%)	12 (0.98%)	8 (0.65%)
Exact match in position & orientation	12 (0.24%)	34 (0.69%)	1 (0.08%)	2 (0.16%)

[i] • : Pre-inked stamp with round housing

■: Self-inking stamp with square housing

Table 4.

Conversion rate of stamp impressions.

	No. of pairs of stamp impressions (%match)
	SET 1 •	SET 2 ■	SET 3 •	SET 4 ■
	With signatory line		Without signatory line
Group A: Exact match in position	3.2%	3.1%	0.98%	0.65%
Group B: Exact match in position & orientation	0.24%	0.69%	0.08%	0.16%
Conversion rate	7.5%	22.3%	8.2%	24.6%

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DOI: https://doi.org/10.69525/jasqde.268 | Journal eISSN: 1524-7287

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Language: English

Page range: 33 - 40

Published on: Dec 1, 2020

Published by: American Society of Questioned Document Examiners

In partnership with: Paradigm Publishing Services

© 2020 Yan Wen Crystal Tan, Hui Ying Yvonne Sim, Chin Chin Lim, Chiew Yung Yang, published by American Society of Questioned Document Examiners
This work is licensed under the Creative Commons Attribution 4.0 License.

Volume 23 (2020): Issue 2

A Preliminary Study on Stamp Impressions with the Same Placement and Orientation on Reproduced Documents—How Easily can it be Achieved by Deliberately Stamping at the Same Relative Position and Orientation?

Figures & Tables

Figure 1.

Figure 2.

Table 1.

Table 2.

Figure 3.

Figure 4.

Table 3.

Table 4.

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