The 5003 is a 3-band EQ based on the API 553 for the 500-series.  Each band is switchable between two different frequencies and can provide up to 15dB of boost or cut.

Images courtesy of Peter Cornell

Notable Features:

• Inductor-based
• Output transformer similar to the API 2503
• Accepts any 2520-style opamp

Price: No products currently available

More information:

• Schematic available on the project thread at GroupDIY.
• The White Market ordering thread.