Unrelated to the character, but is it sure that the corresponding reading is "vại"?

That's an interesting question regarding "vại" (jar). The reading comes from Prof. Hồng's "Tự Điển Chữ Nôm Dẫn Giải" (http://www.nomfoundation.org/nom-tools/Tu-Dien-Chu-Nom-Dan_Giai/Tu-Dien-Chu-Nom-Dan_Giai). I'm not familiar with the Jing dialect of Vietnamese spoken in China, but the IPA reading given corresponds to "standard" Vietnamese "đậy" (cover, put a lid on). As the evidence shows, "đậy" also means "cover" in Jing, but in Vietnamese Nôm it is more commonly written 𢂌, 帒, 待, etc. "Đậy" is also a valid reading for VN-F0B1F in standard Vietnamese as shown in the entry below from "Đại Tự Điển Chữ Nôm". I suspect that Prof. Hống's interpretation as "vại" is based on the context, a list of earthenware vessels, and the Hán-Việt reading of the final of 代 "đại"