Bankers' marks were a way to differentiate official coinage from counterfeit, and perhaps had other purposes that are lost (at least to me). While I don't know why this coin was marked, I am glad that the marks made this particular coin less desirable to some potential auction bidders.
The obverse shows Juno Moneta and the reverse, tools used to make coins: tongs, anvil, garlanded die (or perhaps the cap of Vulcan) and a hammer. There are bankers' marks on both sides, and in both cases, as I see it, they do not interfere with the main elements. The one on the reverse almost looks like another tool that belongs there.
T. Carisius, 46 BC, AR Denarius (18mm, 3.83g), Rome mint
Obv: Head of Juno Moneta right; MONETA to left
Rev: Implements for coining money: anvil die with garlanded punch die above, tongs and hammer on either side; all within laurel wreath.
Ref: Crawford 464/2; CRI 70; Sydenham 982b; Carisia 1b
Little is known about the moneyer, Crawford notes that he is perhaps the Carisius mentioned by Appian:
"Octavian placed all of his infantry under charge of Cornificius, and ordered him to drive back the enemy and do whatever the exigency required. He himself took ship before daylight and went seaward lest the enemy should enclose him on this side also, giving the right wing of the fleet to Titinius and the left to Carisius, and embarking himself on a liburnian, with which he sailed around the whole fleet, exhorting them to have courage."
-Appian Civil Wars 5.112
A temple to Juno Moneta (Juno "the Advisor" or "Warner") was dedicated on the Capitoline Hill in 344 BC where the house of Manlius Capitollinus had stood. L Furius Camillus had made a promise to build a temple to Juno Moneta during a battle with in 345 with the Aurunci.
"After the Dictator had taken the auspices and issued orders for the soldiers to arm for battle, he uttered this prayer: ‘Pythian Apollo, guided and inspired by thy will I go forth to destroy the city of Veii, and a tenth part of its spoils I devote to thee. Thee too, Queen Juno, who now dwellest in Veii, I beseech, that thou wouldst follow us, after our victory, to the City which is ours and which will soon be thine, where a temple worthy of thy majesty will receive thee.’ After this prayer, finding himself superior in numbers, he attacked the city on all sides, to distract the enemies' attention from the impending danger of the mine."
Titus Livius (Livy), The History of Rome, Book 5.21
The Temple to Juno Moneta housed the Roman mint, as well as archives and standards. The word "moneta" became associated with the coins and the root of our word "money". The site where it once stood, is today the site of the Basilica di Santa Maria in Ara Coeli.
Edited image with a detail from Plan of Rome, from Professor G. Droysen's "Allgemeiner Historischer Handatlas", 1886.
Here is interesting article on the origins, and significance of Moneta and the siting of the mint of Rome: Moneta and the Monuments: Coinage and Politics in Republican Rome by Andrew Meadows and Jonathan Williams, Department of Coins and Medals, The British Museum, Journal of Roman Studies, Volume 9, November 2001, pp. 27-49.