ˌcopper-ˈbottomed adjectiveadj able to be depended on 完全可靠的，稳妥保险的 a copper-bottomed guarantee 可靠的保证
copper-bottomed• This was not only copper-bottomed security, it was a chance to play with the big numbers and see what happened.
From Longman Business Dictionary
copper-bottomedˌcopper-ˈbottomed adjectiveadj completely safe to buy, invest in, or have confidence inState pensions are supposed to have a copper-bottomed guarantee.