Verb tense: This [is] or [was]

I have made up the two sets of my examples below.

(1a) John, look at my colorful postage stamp here. This is the very first one I have in my collection.

(1b) John, look at my colorful postage stamp here. This was the very first one I have in my collection.

(2a) Bill, take a look at all these old vases in the museum. The one with a dragon design is the very first one ever made.

(2b) Bill take a look at all these old vases in the museum. The one with a dragon design was the very first one ever made.

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My non-native English speaking friends think they are all correct except one minor thing. In both versions of (1), I have to say "had".

I am not sure if my friends are really correct. Please help me out. Thank you very much for all your time and help.