What kind of guitar pick did Stevie Ray Vaughan prefer?

Context: Vaughan bought many Stratocasters and gave some away as gifts. A sunburst Diplomat Strat-style guitar was purchased by Vaughan and given to his girlfriend Janna Lapidus to learn to play on. Vaughan used a custom set of uncommonly heavy strings, gauges.013,.015,.019,.028,.038,.058, and tuned a half-step below standard tuning. With these heavy string sizes, it was not uncommon for him to separate his fingernail because of his quick movement along the strings. The owner of an Austin club recalled Vaughan coming into the office between sets to borrow super glue, which he used to keep a fingernail split from widening while he continued to play. The super glue was suggested by Rene Martinez, who was Stevie's guitar technician. Martinez eventually convinced Stevie to change to slightly lighter strings. He preferred a guitar neck with an asymmetrical profile, which was more comfortable for his thumb-over style of playing. Heavy use of the vibrato bar necessitated frequent replacements; Vaughan often had his roadie, Byron Barr, obtain custom stainless steel bars made by Barr's father. As for his usage of plectrums, Vaughan preferred Fender medium gauge guitar picks, using one of the rounder shoulders of the pick rather than the pointed tip to pluck and strum the strings.

Answer: SRV is known to have used Fender's medium gauge picks, but with an interesting quirk - he preferred the rounder edge over the pointy tip, which most players use.