I know this coin has been covered extensively in the forum yet I had a chance to scan my Tallero and Maria Theresia coins which I own and share with the forum a bit about their inter-linked history.
The Italians and Maria TheresaIn one of the great number of stories about this coin, the Italians introduced a "tallero" with .8139 ounce of silver into their new colony of Eritrea in 1890/1 in direct competition with the .752 oz Maria Theresa. Austria's Maria Theresia Taler held its ground.


In 1918 they introduced another tallero (see scan above), this one at .7535 and sporting an image imitating Maria, did equally poorly. The Ethiopians were just used to the Maria Theresia and would only accept it--or they would accept the others at a significant discount to the Maria Theresa value.


Between 1935 and 1937 the Italians minted no less than 18 million Maria Theresa to finance their invasion of Ethiopia and subsequent Italian East Africa (AOI) Colony. Maria was the only coin accepted. Between November 28, 1934 and August 15, 1935 the official exchange rate dropped from 4.75 lire per thaler to 9 per thaler. By October it was 12.5 lire per thaler.
After their occupation of Ethiopia, the Italians declared the Lira the official coin of the new colony and would give out five for each thaler (the 5 lire coin weighed 1/5 of the thaler!). They would not give thalers for lire. They wanted to eradicate the Maria Theresa and establish the lira as the only currency.
By February, 1937, the official rate was back up to 10.50; it rose again June 11 to 13.50. The black market value ranged about 5 lire over the official rate. In reality, the thaler was in demand and the lira was not. By 1940 as the Italians were about to be ousted by England the rate was around 30 lire to the thaler.
This is just one of the many, many incidents in the life of the great lady of Austria on one of the most successful coins ever made.