Netherlands East Indies. (Singapore). 1940. Air Mail envelope addressed to s'Gravenhage bearing Netherlands Indies SG 405, 20c purple tied by Soerabaya date stamp '7th March 40', routed via Singapore with 'Passed by censor' label tied by framed 'Passed by/ Censor/ 29/ Censor' cachet with circular '10' in violet on face. Very fine.
The single numeral censor appears to have been applied to mail in transit from Singapore in early 1940.