SECTION 1. Notwithstanding the provisions of this chapter or any other general or special law, rule or regulation to the contrary, a member in service of a retirement system as defined in section 1, or any judge or justice eligible for retirement benefits pursuant to M.G.L c. 32 sects. 65A-65J, shall be provided written notice by the retirement board upon entry into service that if they qualify as a veteran who served in the armed forces of the United States, they shall be entitled to credit for active service in the armed services of the United States; provided, however, that such active service shall not be credited until such member, prior to or within 1 year of vesting pursuant to this chapter, has paid into the annuity savings fund of such system, in 1 sum or in installments, upon such terms and conditions as the board may prescribe, makeup payments, for each year of creditable service sought, of an amount equal to 10 per cent of the regular annual compensation of the member when said member entered the retirement system; and, provided further, that such creditable service shall not be construed to include service for more than 4 years; and provided further, that such creditable service shall not be allowed for any period of active service for which said veteran has received credit pursuant to this paragraph. This paragraph shall apply to national guard and active reserve personnel, both former and present. Creditable service time, both enlisted and commissioned, may be applied toward retirement on a ratio of five 5 years of national guard service or 5 years of active reserve service substitutable for each year of active service. National guard and active reserve personnel shall not be precluded from making said purchase if they qualify as a veteran after vesting or if they reach the maximum of 4 years of eligible service purchase after vesting and qualifying as a veteran; provided, however, that they enter into a purchase agreement within 5 years of the last occurring event.