He must have signed thousands of them. In fact he got sued by his neighbor Ray Stevens around that time because the tour buses would constantly be coming to Webb’s house to see it, the pool, and Webb, and that’s where 90% of all those signed albums come from.

I don’t have any info on that particular record, but did find a picture of Webb with the mailbox (the same picture on your cover?) at the Heart of Texas Country Music Museum site. It’s about halfway down the right column on this page.

Pierce didn’t have another Billboard #1 during the 1960s but he had eight top five records, seven that landed between 6-10, another nine that landed in the top 20 and 13 more tht landed somewhere in the top 40. That’s 37 top forty records which is more chart action than many artists have in a whole career

Although not reflected in the Billboard data, two of Webb’s records hit #1 on Cashbox or Record World. Cashbox was the top competor to Billboard and was as highly regarded as Billboard during the span of Pierce’s career. A lot of country radio stations kept their own charts, but those that didn’t were as likely to use Cashbox’s charts for their countdown shows as to use
Billboard’s charts.

He was out of favor by the ’60s and his records did not chart well. Webbe had zero No. 1 hits in the ’60s and Merle Haggard must have had more than half a dozen–but that Billboard chart rates Webb higher than Merle for the ’60s. Ridiculous.