What are the requirements for the vessel used to wash the hands of the kohanim before birkas kohanim?

Question

The hands of the kohanim are washed before birkas kohanim.

Mishnah Berurah 128:21

(כא) עד הפרק - ככהן המקדש ידיו לעבודה [רמב"ם]. וע"כ כתבו האחרונים דאפשר דבעינן דוקא נטילה מכלי וכח גברא ושלא יהיו משתנים המים מברייתן ויהיה עכ"פ רביעית מים

says that the Acharonim wrote that it is possible that one needs washing from a keli etc.

In a couple of synagogues, I have seen silver vessels used which were brought to the UK by refugees from mainland Europe.

Both the silver vessels did not have a perfectly circular area from which to pour but rather had a spout, level with the rest of the vessel as in the drawing (view from on top of the vessel).

Kitzur Shulchan Oruch 40, 2 seems to exclude such a vessel (for washing for bread) when it says:

נְטִילַת יָדַיִם צָרִיךְ לִהְיוֹת דַּוְקָא מִן הַכְּלִי. וְצָרִיךְ שֶׁיִּהְיֶה הַכְּלִי שָׁלֵם בְּלִי שׁוּם נֶקֶב אוֹ סֵדֶק מְפֻלָּשׁ. וְגַם לְמַעְלָה יִהְיֶה שָׁוֶה בְּלִי שׁוּם חָרִיץ אוֹ בְּלִיטָה

Washing needs to be specifically from a vessel which should have no hole or crack and at the top should have no groove or protrusion

What then are the requirements for the vessel used to wash the hands of the kohanim before birkas kohanim?

Answer 1

In short, there are none, but we're generally stringent to follow the regular regulations for Netilat Yadayim.

Though there are no such requirements mentioned in the Gemara or Rishonim, the Acharonim suggest that there may be reason to require a vessel in accordance with the standard procedure of Netilat Yadayim for a meal. They include Magen Avraham (128:8), Shulchan Aruch HaRav (128:8), Ben Ish Chai (Shanah Rishonah, Parashat Teztaveh 8), Mishnah Berurah (128:19), Kaf HaChaim (128:43), Rav Mordechai Eliyahu's comments on Kitzur Shulchan Aruch 100:7, and Ashrei HaIsh (vol. 1, 23:1, page 121).

The Aruch HaShulchan (128:15) claims it's self-evident, while the Halacha Sedurah (contemporary thin volume on Birkat Kohanim and other Tefillah Topics, vol. 2 5:4) is unsure but concludes that Safek Derabbanan LeHakel. Piskei Teshuvot (128:21) asserts it's certainly not LeIkuva, especially in light of the fact that one who kept his hands clean all morning since he washed, even without all the Hiddurim, may go up without washing altogether. (Note footnote 92 there which may contradict what he says on top)