I don’t know th eage of my detached garage roof, will insurance cover?

Hello,

My detached garage roof collapsed. I submitted a claim to TD Bank (Canada). They have sent a Contractor to assess, the Contractor requested an Engineer to assess, the Engineer is coming today.

My house was built in 1945. I don't know when my garage was built. I have a survey plan of 1968 where my garage is shown.

If the Insurance company requests proof of the age of the roof, how can I prove it? What if I am not able to prove it, they will reject my claim? Can I just say it as old as the house, what implications would be?