The numbering of houses, buildings and places of business provided for in Section 12.20.010 shall be in conformity with the following rules:
A. Main Street shall be the base from which the numbering of all houses, buildings and places of business facing on the streets and avenues running east and west shall begin.
B. First Street shall be the base from which the numbering of all houses, buildings and places of business facing on the streets and avenues running north and south, shall begin.
C. Every lot or portion thereof amounting to twenty-five feet of frontage on any of the streets or avenues shall be entitled to one whole number, which shall in all cases be counted in determining the appropriate number or numbers of any house or houses, building or buildings or place or places of business in the same block, whether the place shall have any such house, building or place of business occupying the same or not; provided, that where two or more houses, buildings or places of business occupy the same twenty-five feet of frontage space, the number applicable to such space shall appear upon each house, building or place of business, and to designate the same, the letters of the alphabet shall be used following the last numeral of the number, beginning with the letter “A” and going down the alphabet in regular succession until all such houses, buildings or places of business shall be properly designated; and provided further, that all doorways or archways leading to stairways or elevators shall be numbered by adding a common fractional number to the whole number next toward the base therefrom. (Prior code § 5-41).