Is it a commando or MRS?Its not just when it was bought its when it was manufactured.
To be honest I would think hard before buying a Sig. There is no after market support so upgrades are not as plentiful as on M4's, AK's or other more common models. The Ics Sig is great gun but it is flawed, it has probably the best stock V3 gearbox on any gun but a lot of it is proprietary.
If your thinking of upgrading its not a good choice. I am part way through rebuilding/customising one so have some custom parts spare if you have really deep pockets.