Original: Gray was also interested in postage stamps; on 1 May 1840, the day the Penny Black first went on sale, he purchased several with the intent to save them, thus making him the world's first known stamp collector.
Simplified: Gray was also interested in postage stamps; on 1 May 1840, the day the Penny Black first went on sale, he bought some to keep, thus making him the world's first known stamp collector.