Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
How much was a Reverse of guitar of agustín pío barrios before 1998?

### Inputs:
table_name: table, columns: ['Value', 'Color', 'Obverse', 'Reverse', 'First issued']

### Response:
SELECT Value FROM table WHERE First issued < 1998 AND Reverse = guitar of agustín pío barrios