Each fire insurance company incorporated under the laws of this state or legally authorized to do business in this state, whose property is under the law subject to ad valorem taxation by the city, shall render for taxation by the city all of its real estate as other real estate is rendered and all of the personal property of such insurance company shall be valued as other personal property is valued for assessment for taxation by the city in the following manner. From the total valuation of its assets shall be deducted the legal reserves required to be maintained by it under the laws of the state and from the remainder shall be deducted the assessed value of all real estate owned by the company and the capital stock of such company, except in case its surplus should not equal 50 percent of its capital stock, then only 50 percent of its capital stock shall be deducted, and the remainder of the valuation of its total assets, after the deduction of the assessed value of its reserves, its real estate and its capital stock, in whole or in part as herein provided, shall be the assessed taxable value of its personal property. The surplus provided for in this section shall be computed for the purpose of taxation whether the same constitutes or is made up, in part or in whole, of exempt securities under law, it being the purpose of this section to provide a method for arriving at the proper assessment of such companies irrespective of the character of property constituting the same. (Code 1941, Art. 148-2)