An adjective implied by the name Q. Telpinquar “Silver-fist”, the Quenya equivalent of S. Celebrimbor in notes from the mid-1960s (PE17/42). In other writings Tolkien gave this name as (archaic) Tyelpinquar (PM/318; VT47/8). It is conceivable that this adjective is t(y)elpin, but both The Etymologies of the 1930s of the 1930s and the Qenya Lexicon of the 1910s, Tolkien had ᴹQ. telpina (Ety/KYELEP) and ᴱQ. telpina “of silver” (QL/91), so I think the late form of this adjective is more likely telpina as a combination of telpë “silver” with the adjective suffix -ina “silver”.

Conceptual Development: In the Qenya Lexicon, ᴱQ. telpina was glossed “of silver” and had variants ᴱQ. telpea, telpia and {telpeksa}, the last of which was deleted (QL/91). In The Etymologies of the 1930s ᴹQ. telpina was equated to ᴹQ. telepsa “of silver”, but telepsa was deleted and no gloss was provided after these revisions (Ety/KYELEP). In the mid-1960s note mentioned above, Tolkien said of S. celebrin that it was “not implying ‘made of silver’ but ‘like silver’ in hue, or worth” (PE17/42), but it is not clear whether the same applies to Q. telpin[a].

Finally, there was a longer Quenya name Telperinquar for S. Celebrimbor in the mid-1960s note (PE17/42), implying a variant Quenya adjective telperin that was a more direct equivalent of S. celebrin.

Neo-Quenya: For purposes of Neo-Quenya, I would assume telpina is a general adjective “silver” than can mean either “made of silver” or “like silver”, while longer telperin more specifically means “like silver in hue or worth”.