It goes back to a famous incident in 1703. The rabbi of the Sefardic congregation Sha'ar Hashamayim in London, David Nieto, had given a sermon in which he said that God is nature and nature is God. Or at least that's how his accusers framed it when they accused him of pantheism, which was Spinoza's heresy. Historians have concluded that his accusers were probably motivated by other things, as apparently many heresy hunters are. The sermon itself was actually an argument against Deism, which saw nature as intermediary between God and man. Nieto said that this is contrary to Judaism. That which we now call "Nature" was originally called by the rabbis "God." In other words, now we would talk about an earthquake being an event of nature, whereas Judaism teaches that it is an act of God. If this sounds like apologetics, I would say that it is unlikely that he was promoting Pantheism in his argument against Deism. In addition, in all other respects David Nieto exhibited piety, and was a "zealous advocate of Judaism, the stalwart champion of the oral law," in the words of David Kaufmann, referring to Nieto's Matteh Dan - Kuzari Sheni.
It seems that the Sefardic rabbis of Amsterdam were applied to to mediate the dispute, but they declined to get involved. Controversial Ashkenazi big shot Aberle Hamburger of London, who was respected by London Sefardim, wrote Chacham Zvi, who was personally known by the London Sefardim and respected by them (his name is usually given as "Aberle," but I myself wonder if it was not pronounced "Avrele). We know this from the book Urim ve-Tumim by R. Uri Shraga Pheobus Hamburger of London, printed in 1707:
In any event, you can see that Chacham Zvi replied that the disputants should send him letters
explaining their sides. Can you imagine? He said that he would not give his reply in a dispute over heresy until he heard both sides?
To summarize: Nieto says that his idea comes straight out of Psalm 147, and that the word "nature" is only 4 or 500 years old (which shows that he had a sensitive linguistic ear). If there formerly was no word "nature," and all understood that God causes everything in nature, then there really is no such independent thing called "nature." All is Divine Providence.
This was done, and several months later Chacham Zvi returned his reply, in which he vindicated Nieto completely and that seems to have ended the matter. When Chacham Zvi printed his responsa in 1712, his reply was included as #18 (along with Nieto's own words explaining what he had said).
Chacham Tzvi replies that Nieto's words are the same as the Kuzari in 1:76 and 77 as explained by R. Judah Moscato. He then gives him a yasher koach for giving such a sermon, which shows that he knows the views of the philosophers on nature, and rejects their bad opinion and accepts the good opinions of our sages. He doesn't understand what the complainers are complaining about. He offers some suggestions as to what their problem may be, and rejects them. Then he quotes the Shnei Luchos Habris (a book which the whole Jewish world accepts lovingly, notes Chacham Zvi) who in turn quotes the author of Avodas Hakodesh (whom Chacham Zvi notes was a Sefardi) to the effect that the rewards and punishments for those who do or spurn mitzvos are natural. He end by congratulating Nieto, wishing him good luck, and warns that those who keep accusing him after this are to be suspected of sinners.
Finally, he closes by noting that although these points are clear and certain, to strengthen the vindication he invited two great talmidei chachomim of his city, Altona, to discuss the matter with him, and they all agreed with his words.
In the She'elos U-Teshuvos Chacham Tzvi the responsum is signed צבי אשכנזי ס"ט בהרב המובהק כמוה"רר יעקב זלה"ה and the names of the two scholars he consulted are not given. However, the response was not first printed in 1712. The responsum is dated 15 Av 5465, and it was circulated in print in a special pamphlet printed in London in Elul. Here is the cover of the pamphlet:
Here is how it is signed at the end:
Thus, we can see that the responsum was actually co-signed by the aforementioned two talmidei chachomim, who were R. Shlomo ben Nathan and R. Aryeh ben Simcha of Vilna S"T (ס"ט). Interestingly, Chacham Zvi himself does not sign with ס"ט here. I was tempted to say that it's a printer error, and mistakenly it was omitted from his name and added to R. Aryeh ben Simcha of Vilna, but in fact the pamphlet was printed twice. I have copies of both and there are slight differences, which show that the type was set a second time, and both are signed exactly the same way. Also, even though it was printed by the Sefardim in London, there should be no grounds for saying that they added it, because there is no reason to apply it after the name of one but not all. Furthermore, Sefardim certainly were well aware that Sefardim used S"T but not Ashkenazim, at least not generally.
Thus, I believe we have another example of an Ashkenazi using S"T, this one from Vilna. Most interestingly, his signature appears juxtaposed with Chacham Zvi's, who does not use it here.