Overprints	A T Ms	Additional Stamp Impressions	Design Prints	Sheet Stamps	Print Substrates	Roulettings	Punches	Separate Productions	Meter Stamps	Postal Stationeries
Cliche Cancellations	Gums	Pencancel- lations	Hand Postmarks	Tress Rosettes	Lumines- cences	Stamp Booklets	Machine Postmarks	Embossings	Press Marks	Margin Prints
Reverse Prints	Silk Threads	Die-cuttings	Ink Jet Can- cellations	Stamped Envelope Overprints		Burelages	Form Prints	Watermarks	Stamp Impressions	Perforations
Se-tenants	Second Overprints		Others

Knowledge / Errors / Gums

Gum Error: philatelic term for a deviation caused by a gum error

Gum Colour Error: deviation from the intended gum colour caused by an error

Design Print on Reverse: postage stamp with design print on reverse instead on front

Missing Gum: postage stamp without gum caused by an error

Vertical Instead of Horizontal Ribbed Gum: postage stamp with 90 degrees rotated ribbed gum

Horizontal Instead of Vertical Ribbed Gum: postage stamp with 90 degrees rotated ribbed gum

Bark Gum: unregular thick and grazed gum