Find all real numbers $a$ for which the equation $x^2a- 2x + 1 = 3 |x|$ has exactly three distinct real solutions in $x$.
To find all real numbers \( a \) for which the equation \( x^2a - 2x + 1 = 3 |x| \) has exactly three distinct real solutions in \( x \), we will analyze the equation by considering the cases \( x = 0 \), \( x > 0 \), and \( x < 0 \).

1. **Case 1: \( x = 0 \)**
   \[
   a \cdot 0^2 - 2 \cdot 0 + 1 = 3 |0|
   \]
   \[
   1 = 0
   \]
   This is clearly not true, so there are no solutions for \( x = 0 \).

2. **Case 2: \( x > 0 \)**
   For \( x > 0 \), \( |x| = x \). The equation becomes:
   \[
   ax^2 - 2x + 1 = 3x
   \]
   Simplifying, we get:
   \[
   ax^2 - 5x + 1 = 0
   \]
   The solutions to this quadratic equation are given by the quadratic formula:
   \[
   x = \frac{5 \pm \sqrt{25 - 4a}}{2a}
   \]
   For the equation to have real solutions, the discriminant must be non-negative:
   \[
   25 - 4a \geq 0
   \]
   \[
   a \leq \frac{25}{4}
   \]

3. **Case 3: \( x < 0 \)**
   For \( x < 0 \), \( |x| = -x \). The equation becomes:
   \[
   ax^2 - 2x + 1 = -3x
   \]
   Simplifying, we get:
   \[
   ax^2 + x + 1 = 0
   \]
   The solutions to this quadratic equation are given by the quadratic formula:
   \[
   x = \frac{-1 \pm \sqrt{1 - 4a}}{2a}
   \]
   For the equation to have real solutions, the discriminant must be non-negative:
   \[
   1 - 4a \geq 0
   \]
   \[
   a \leq \frac{1}{4}
   \]

To have exactly three distinct real solutions, one of the quadratic equations must have a double root (discriminant equal to zero) and the other must have two distinct real roots. 

4. **Scenario Analysis:**
   - **Scenario 1:** The discriminant of \( ax^2 - 5x + 1 = 0 \) is zero.
     \[
     25 - 4a = 0
     \]
     \[
     a = \frac{25}{4}
     \]
     Substituting \( a = \frac{25}{4} \) into \( ax^2 + x + 1 = 0 \):
     \[
     \frac{25}{4}x^2 + x + 1 = 0
     \]
     The discriminant is:
     \[
     1 - 4 \cdot \frac{25}{4} = 1 - 25 = -24
     \]
     This results in no real roots, so this scenario is not possible.

   - **Scenario 2:** The discriminant of \( ax^2 + x + 1 = 0 \) is zero.
     \[
     1 - 4a = 0
     \]
     \[
     a = \frac{1}{4}
     \]
     Substituting \( a = \frac{1}{4} \) into \( ax^2 - 5x + 1 = 0 \):
     \[
     \frac{1}{4}x^2 - 5x + 1 = 0
     \]
     The discriminant is:
     \[
     (-5)^2 - 4 \cdot \frac{1}{4} \cdot 1 = 25 - 1 = 24
     \]
     This results in two distinct real roots.

Therefore, the value of \( a \) that satisfies the condition is \( a = \frac{1}{4} \).

The final answer is \( \boxed{\frac{1}{4}} \).