If any person who has received a refund is reemployed by an Employer and again becomes a contributor for a period of at least 2 years, or has established credit of at least 2 years of service subsequent to the date of such refund, in a retirement system which has subscribed to the “Retirement Systems Reciprocal Act” and is a contributor thereto, he may repay to the Fund the amount he received as a refund, together with interest thereon at 5% per annum compounded annually from the time the refund was paid to the date of repayment.