Once Zenith had made the transition from handwired chassis to the printed circuit boards, the second generation was born (the 500B). It was at this time that they expanded the color selection to include the white, tan, and pink versions. Along with the Black and Maroon color selections, each of the five colors could be produced with any one of 3 the chassis types: 7ZT40, 7ZT40Z1, and the scarcest was the 7ZT40Z with the blue Raytheon transistors.
Replacement cost of the transistors from Sylvania (7ZT40) and Texas Instruments (7ZT40Z1) averaged $2.75 each ($19.00 for the 7). The Raytheon transistors (7ZT40Z) cost $5.25 ($36.75 for the 7) or a profit reduction of $17.75 per radio. No matter which one you bought, the selling price was still set at $75.00 so Zenith naturally limited the use of them as much as possible.*
Although there are no official numbers that anyone I have talked with has found, it is estimated that only about 5% of the total production run had the 7ZT40Z chassis.
An interesting point to note is that by the time the 500H came out in 1961, the cost of a transistor had fallen 40% to $1.67 each.)**
*Data is from the official Supplementary Service Manual number 2 for Zenith Royal 500 Chassis 7ZT40 revised & 7ZT40Z using replacement part selling prices.
**Data is from the official Zenith Service Manual for Model Royal 500H chassis 8HT40Z2 using replacement part selling prices.