The (incontrovertably socialist) Russian provisional government designed the banknotes with the fylfots represented. This is not seriously disputed. It may be unseriously disputed, I suppose.
The unique nature of the Socialist fylfot may be because socialism was regarded as an international movement, as Communism was later. But a socialist symbol it was, without question.
The provisional government was most definitely NOT comprised of any Soviets. As matter of fact, Soviets were a parallel power structure, with their own armed forces, and wanted nothing to do with Provisional government; that's why they finally overturned it.
But if there are doubts still, let's see what Provisional government actually did while it was in power:
It postponed the expected elections. Instead of ending Russia's involvement in World War I, it launched a new offensive against the German and Austro-Hungarian army in July 1917, thereby weakening its popularity among Russia's war-weary people. The Provisional Government was unable to make decisive policy decisions due to political factionalism and a breakdown of state structures.[5] This weakness led to a challenge from the right in the form of the Kornilov Affair, and then from the left, which organized the October Revolution
I don't see any socialism here, really, just a complete failure, equally despised by the right and the left. It's not even possible to attach any rational policy to this government, aside from the need to "do something."