In preparation for the introduction of pre-paid postage stamps in May 1840, standard (or common) Maltese cross obliterators were issued to all post offices in April 1840. Although they were all made to a common pattern, as each one was made by hand no two were exactly alike.
From 1840 to 1844 the One Penny and Two Penny line engraved stamps of Great Britain were cancelled with this common cross obliterator. For the first few months, red ink was used for obliterating and black ink thereafter. It follows that Maltese crosses in red were made with the original obliterators are, almost without exception, common crosses. Red crosses are found mainly on the early One Penny black and Two Penny blue stamps, although there are exceptions to be found on One Penny red stamps.
Instructions for preparing the red ink (or ‘composition’ as it was called at the time) were sent out with the original obliterators for every Post Office to mix their own. (“One pound of printer’s red ink; one pint of linseed oil, and a half pint of the droppings of sweet oil – to be well mixed.”)
As these ingredients would have been purchased locally and mixed by hand, the resulting colour varies considerably in its shade from brown, red-brown and red, to bright red and orange. There are also some other rare coloured crosses, of which blue is the most often found.
Maltese crosses in black are much more common as they were in use for over three years, and are found on Penny blacks (plates 1 to 11), Twopenny blues (plates 1 to 3) and Penny reds (plates 1 to 45).
Inevitably the need arose, from time to time, for obliterators to be replaced or supplemented, and often a local craftsman was employed to provide a copy of the original. Some were good copies and others not so.
The not so good copies, while following the general pattern, introduced variations which were often unique. The Maltese cross they produced would show a constant variation from the common cross, from which the issuing post office can often be identified - if there were enough on cover examples to establish their identity initially.
If a Maltese cross can be identified off cover and attributed to a particular Post Office, it is referred to as being distinctive. Distinctive crosses are normally black and found mainly on Penny reds and much less often on Penny blacks and Twopenny blues.
There are many crosses with ‘distinctive’ features which cannot be attributed to a particular Post Office – usually because too few examples have been found on cover to confirm if the ‘distinctiveness’ is constant. Often, such apparent distinctiveness can be due to transient inking or striking anomalies.