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The past tense of "conceal" is "concealed."
The surface of the table was very rough, it had a lot of imperfections
"He was allowed to conceal his firearm, since he had a license."
"As a hunted fugitive, he had to conceal his identity."
The present tense of "conceal" is "conceals" for third person singular (he/she/it) and "conceal" for all other subjects.
She tried to conceal her true emotions behind a smile.