The purpose of this app is to allow guitar enthusiasts to catalog and view their gear. I broke up the gear into three different models: guitars, amps, and pedals. Guitars have model, manufacturer, and category (acoustic, electric, bass, etc.) attributes. Amps ended up having a lot: name, power type, watts, number of speakers, number of channels, speaker size as well as name and manufacturer. Pedals were just name, manufacturer, category, and power supply requirements.
Back in high school, I used to spend a lot of time buying and selling guitar effects pedals on Craigslist. I would check Craigslist regularly to see if there were any good deals on items that I had my eye on. Since I didn’t have a lot of free cash to spend on this pricey hobby, I often had a one-in-one-out sort of philosophy, selling one pedal to buy another or just trading with someone. In doing these transactions, a bit of research was required. The new price for the pedal, assuming it was still in production, was certainly a factor in resale value. The other main indicator was the price at which other people were selling the same or similar item.