correct tense [are/were/have been appraised]

[ansonman]

I have made up the sentences below.

(1a) I am impressed by your collection of postage stamps. Most of them are appraised by ABC and the rest are appraised by DEF.

(1b) I am impressed by your collection of postage stamps. Most of them were appraised by ABC and the rest were appraised by DEF.

(1c) I am impressed by your collection of postage stamps. Most of them have been appraised by ABC and the rest have been appraised by DEF.

Most of my friends think the simple present is the best. I am not sure if they are correct. Please help me. Thank you.

[Alan]

All are grammatically sound, but (c) is clearly the most natural/likely.