Some of the pre-Shoah Yeshivot in Europe did have bochurim in “modern” dress. I have seen photos of bochurim in straw hats, bow ties and striped suits. I assume that the choice of wearing a regular tie vs. a bow tie did not carry much significance. It was the clothing that was considered respectable in goyish society. However, photos of bochurim at other yeshivot show a different dress code, so their rosh yeshivah probably would have judged the dress code followed elsewhere as lax.
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