Section 58. A veteran who has been in the service of the commonwealth, or of any county, city, town or district or any housing authority or any redevelopment authority, for a total period of thirty years in the aggregate, shall, at his own request, with the approval of the retiring authority, be retired from active service at seventy-two per cent of the highest annual rate of compensation, including any bonuses paid in lieu of additional salary or as a temporary wage increase in addition to his regular compensation, and including any maintenance allowance, payable to him while he was holding the grade held by him at his retirement, and payable from the same source.