The structure shown is a composite of seven resonance contributors in which each carbon carries part of the positive charge.
The tropylium ion is frequently encountered in mass spectrometry in the form of a signal at m/z = 91. This fragment is often found for aromatic compounds containing a benzyl unit. On ionization, the benzyl fragment is cleaved off. It (PhCH2+) rearranges to the highly stable tropylium cation (C7H7+).