there are four distinct variations of the M91 Dutch East Indies revolver:
1) the original contract of 3754 revolvers, manufactured from 1894-5 by either WDW (using J.F.J. Bar-supplied parts) or JFJ Bar. Bar had originally agreed to supplycomplete revolvers, but as time progressed, Bar fell further behind schedule, and more and more of the contract had to be completed by WDW. These revolvers were serial numbered from 1 through 3754, and will bear Dutch inspector's/acceptance marks (usually consisting of a crowned "B" on all major parts). They will also usually (notalways) bear issue dates on the left forward side of the frame (1895), along with unit issue marks on the left side of the frame above the grip;
2) the second contract of 2200 revolvers, manufactured entirely by L. Wittich, for a contract issued in 1909; these revolvers continued the serial number range from thefirst series, from 3755 through 5954, and will also bear Dutch inspection/acceptance marks;
3) in 1920, a third contract for M91 revolvers was issued, this time to Vickers-Armstrong of England, for 5830 revolvers for issue to the Dutch East Indies Police. Theserevolvers turned out to be of substandard quality, and had to be sent to Fabrique National of Belgium, to be completely reworked. These revolvers had serial numbers ranging between 1 and 9000 in several blocks, but all bear English proof marks; and
4) private copies of the M91 revolver were also made by Bar, Beaumont, and Munts in Holland, and by Nagant, and Ancion Marx in Belgium; for private sale to Dutch officers and for civilians heading to the Dutch East Indies.